Merge branch 'docs-english'

docs/languages/gmw/en.md

 # English
 
-- [Short Vowels](#short-vowels)
-- [Long Vowels](#long-vowels)
-- [Rhotic Vowels](#rhotic-vowels)
-- [Reduced Vowels](#reduced-vowels)
-- [Diphthongs](#diphthongs)
-- [Split Vowels](#split-vowels)
+- [Vowels](#vowels)
+  - [Short Vowels](#short-vowels)
+  - [Long Vowels](#long-vowels)
+  - [Rhotic Vowels](#rhotic-vowels)
+  - [Reduced Vowels](#reduced-vowels)
+  - [Diphthongs](#diphthongs)
 - [References](#references)
 
 ----------
 
+The following English accents are supported by eSpeak NG and are referenced in
+this document:
+
+| BCP47          | Abbreviation | Accent Name            |
+|----------------|--------------|------------------------|
+| en             |              | British English        |
+| en-029         |              | Caribbean              |
+| en-GB-scotland | ScE          | Scottish English       |
+| en-GB-x-gbclan |              | Lancastrian            |
+| en-GB-x-gbcwmd |              | West Midlands          |
+| en-GB-x-rp     | RP           | Received Pronunciation |
+| en-US          | GenAm        | General American       |
+
+The BCP47 name is the standard language identifier for the accent, used as the
+espeak language name. The Abbreviation is used in the tables below for the IPA
+transcriptions of that accent, and the BCP47 names are used for the eSpeak NG
+phoneme names.
+
+## Vowels
+
 The English language support uses a vowel system based on John Wells' Lexical
 Sets<sup>\[<a href="#ref1">1</a>\]</sup>. These were created by Wells in 1982
 by comparing the Received Pronunciation British (RP) and General American
 (GenAm) accents in use at that time.
 
-The `en` transcriptions listed below are the phonemes used by eSpeak NG to
-transcribe the different lexical sets.
-
-## Short Vowels
+### Short Vowels
 
 | Lexical Set | en    | RP    | GenAm |
 |-------------|-------|-------|-------|
 | STRUT       | `V`   | ʌ     | ʌ     |
 | FOOT        | `U`   | ʊ     | ʊ     |
 
-## Long Vowels
+Additionally, Wells defines the following lexical sets to describe vowels that
+are different in both RP and GenAm:
+
+| Lexical Set | en    | RP    | GenAm |
+|-------------|-------|-------|-------|
+| BATH        | `aa`  | ɑː    | æ     |
+| CLOTH       | `O2`  | ɒ     | ɔ     |
+
+### Long Vowels
 
 | Lexical Set | en    | RP    | GenAm |
 |-------------|-------|-------|-------|
 | THOUGHT     | `O:`  | ɔː    | ɔ     |
 | GOOSE       | `u:`  | uː    | u     |
 
-## Rhotic Vowels
+### Rhotic Vowels
 
 These are vowels that are followed by an `r` that is not part of the next syllable
 when considering the root form of the word containing that vowel.
 
-| Lexical Set | en    | RP    | GenAm |
-|-------------|-------|-------|-------|
-| NURSE       | `3:`  | ɜː    | ɝ     |
-| START       | `A@`  | ɑː    | ɑɹ    |
-| NORTH       | `O@`  | ɔː    | ɔɹ    |
-| FORCE       | `o@`  | ɔː    | oɹ    |
-| CURE        | `U@`  | ʊə̯     | ʊɹ    |
-| NEAR        | `i@3` | ɪə̯     | ɪɹ    |
-| SQUARE      | `e@`  | eə̯     | ɛɹ    |
+| Lexical Set | en    | en-GB-scotland | RP    | GenAm | ScE   |
+|-------------|-------|----------------|-------|-------|-------|
+| NURSE       | `3:`  | `VR`           | ɜː    | ɝ     | ʌɾ    |
+| START       | `A@`  | `A@`           | ɑː    | ɑɹ    | ɐ̟ɾ    |
+| NORTH       | `O@`  | `O@`           | ɔː    | ɔɹ    | ɔɾ    |
+| FORCE       | `o@`  | `o@`           | ɔː    | oɹ    | oɾ    |
+| CURE        | `U@`  | `U@`           | ʊə̯    | ʊɹ    | ʉɾ    |
+| NEAR        | `i@3` | `i@3`          | ɪə̯    | ɪɹ    | iɾ    |
+| SQUARE      | `e@`  | `e@`           | eə̯    | ɛɹ    | eɾ    |
 
 __NOTE:__ `/i@3/` is used for the NEAR lexical set to differentiate it from
 `/i@/` used in words like `million`.
 
-## Reduced Vowels
+Additionally, espeak-ng has the following phonemes for different accents:
+
+| Lexical Set | en    | en-GB-scotland | RP    | GenAm | ScE   |
+|-------------|-------|----------------|-------|-------|-------|
+| TERM        | `3:`  | `3:`           | ɜː    | ɝ     | ɛɾ    |
+| BIRD        | `3:`  | `IR`           | ɜː    | ɝ     | ɪɾ    |
+
+### Reduced Vowels
 
 These are unstressed vowels that differ from the vowels in the main lexical sets.
 
 have merged this with the COMMA lexical set, such that `rabbit` and `abbot`
 rhyme.
 
-## Diphthongs
+### Diphthongs
 
 | Lexical Set | en    | RP    | GenAm |
 |-------------|-------|-------|-------|
-| FACE        | `eI`  | eɪ̯     | eɪ̯     |
-| PRICE       | `aI`  | aɪ̯     | aɪ̯     |
-| CHOICE      | `OI`  | ɔɪ̯     | ɔɪ̯     |
-| GOAT        | `oU`  | əʊ̯     | oʊ̯     |
-| MOUTH       | `aU`  | aʊ̯     | aʊ̯     |
-
-## Split Vowels
-
-These are lexical sets defined by John Wells that are merged with other lexical
-sets in both RP and GenAm, so have split from one of those lexical sets and
-merged with the other.
-
-| Lexical Set | en    | RP    | GenAm |
-|-------------|-------|-------|-------|
-| BATH        | `aa`  | ɑː    | æ     |
-| CLOTH       | `O2`  | ɒ     | ɔ     |
+| FACE        | `eI`  | eɪ̯    | eɪ̯    |
+| PRICE       | `aI`  | aɪ̯    | aɪ̯    |
+| CHOICE      | `OI`  | ɔɪ̯    | ɔɪ̯    |
+| GOAT        | `oU`  | əʊ̯    | oʊ̯    |
+| MOUTH       | `aU`  | aʊ̯    | aʊ̯    |
 
 ## References
 
 1. <a name="ref1"></a> Wikipedia.
    [Lexical set](https://en.wikipedia.org/wiki/Lexical_set). 2017.
    Creative Commons Attribution-Sharealike 3.0 Unported License (CC-BY-SA).
+
+2. <a name="ref2"></a> Wikipedia.
+   [IPA chart for English dialects](https://en.wikipedia.org/wiki/International_Phonetic_Alphabet_chart_for_English_dialects).
+   2018. Creative Commons Attribution-Sharealike 3.0 Unported License (CC-BY-SA).