feat!: Add support for "iw" command

- CLI completion for iw (Linux wireless configuration utility).
- Directly parses "iw help" output to discover commands and caches the result.
- $service is used as the iw binary name. This allows this completion to work
  for differently-named iw binaries: compdef _iw my-iw-binary

plugins/iw/README.md

@@ -0,0 +1,40 @@
+# iw plugin
+
+This plugin adds tab completion for [`iw`](https://wireless.wiki.kernel.org/en/users/documentation/iw),
+the standard Linux command-line tool for configuring wireless network interfaces.
+
+To use it, add `iw` to the plugins array in your zshrc file:
+
+```zsh
+plugins=(... iw)
+```
+
+## Completion
+
+Completion is generated dynamically by parsing the output of `iw help` and cached for
+performance. The cache is stored in `$ZSH_CACHE_DIR/_iw_cache` and is automatically
+regenerated when the installed version of `iw` changes.
+
+The following command structure is completed:
+
+| Level | Examples |
+| ----- | -------- |
+| Top-level commands | `dev`, `phy`, `wdev`, `reg`, `list`, `event`, … (discovered dynamically) |
+| Interface / phy names | `wlan0`, `phy0` (discovered from `/sys/class/net` and `/sys/class/ieee80211`) |
+| Subcommands | `dev <if> scan`, `dev <if> station`, `phy <phy> set`, … |
+| Sub-subcommands | `dev <if> scan dump`, `dev <if> station get`, `phy <phy> set txpower`, … |
+
+## Functions
+
+| Function | Description |
+| -------- | ----------- |
+| `iw-clear-cache` | Delete the cached completion data (useful after upgrading `iw`) |
+
+## Requirements
+
+- `iw` must be installed and in `$PATH`
+- Completion for a differently-named `iw` binary can be enabled with:
+
+  ```zsh
+  compdef _iw my-iw-binary
+  ```