docs/phonemes.md: restructure the co-articulation features.

docs/phoneme_model.md

   - [Air Flow](#air-flow)
   - [Initiator](#initiator)
   - [Target](#target)
+    - [Co-articulation](#co-articulation)
   - [Manner](#manner)
 - [Place of Articulation](#place-of-articulation)
   - [Active Articulators](#active-articulators)
   - [Passive Articulators](#passive-articulators)
+  - [Co-articulation](#co-articulation-1)
 - [Phonation](#phonation)
   - [Voice](#voice)
 - [Vowel Height](#vowel-height)
 | `nsl`   | nasal      | The air flows through the nose.                 |
 | `orl`   | oral       | The air flows through the mouth.                |
 
+#### Co-articulation
+
+| Feature | Name      | Target |
+|---------|-----------|--------|
+| `nzd`   | nasalized | `nsl`  |
+
 ### Manner
 
 | Feature | Name        | Description                                                                       |
 | `egs`   | epiglottis             |
 | `gts`   | glottis                |
 
+### Co-articulation
+
+| Feature | Name            | Articulator |
+|---------|-----------------|-------------|
+| `pzd`   | palatalized     | `hpl`       |
+| `vzd`   | velarized       | `spl`       |
+| `fzd`   | pharyngealized  | `prx`       |
+| `nzd`   | nasalized       | `nsl`       |
+| `rzd`   | rhoticized      | `apc hpl`   |
+
 ## Phonation
 
 The phonation features describe the degree to which the glottis (vocal chords) are open or closed.

docs/phonemes.md

   - [Rounding and Labialization](#rounding-and-labialization)
   - [Syllabicity](#syllabicity)
   - [Consonant Release](#consonant-release)
+  - [Co-articulation](#co-articulation)
 - [Features](#features)
   - [Fortis and Lenis](#fortis-and-lenis)
-  - [Co-articulation](#co-articulation-1)
   - [Suprasegmentals](#suprasegmentals)
     - [Stress](#stress)
     - [Length](#length)
 | `lrs`   | ◌ˡ     | lateral release                 |
 | `unx`   | ◌̚      | no audible release (unexploded) |
 
-## Features
-
 ### Co-articulation
 
-| Feature | Symbol | Name            | Co-Articulator | Type                  |
-|---------|--------|-----------------|----------------|-----------------------|
-| `pzd`   | ◌ʲ     | palatalized     | `hpl`          | Passive Articulator   |
-| `vzd`   | ◌ˠ     | velarized       | `spl`          | Passive Articulator   |
-| `fzd`   | ◌ˤ     | pharyngealized  | `prx`          | Passive Articulator   |
-| `nzd`   | ◌̃      | nasalized       | `nsl`          | Target                |
-| `rzd`   | ◌˞     | rhoticized      | `rfx`          | Place of Articulation |
+| Feature | Symbol | Name           |
+|---------|--------|----------------|
+| `pzd`   | ◌ʲ     | palatalized    |
+| `vzd`   | ◌ˠ     | velarized      |
+| `fzd`   | ◌ˤ     | pharyngealized |
+| `nzd`   | ◌̃      | nasalized      |
+| `rzd`   | ◌˞     | rhoticized     |
+
+## Features
 
 Additionally, the tongue root position can be specified using the following
 features: