Add ready-to-use example modules

examples/modules/ ships complete, drop-in bread modules for common desktop
automations (low-battery warning, pause-media-on-headphone-unplug,
dock-monitors) plus a README on installing them. Complements Examples.md,
which teaches the porting patterns.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

examples/modules/README.md

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+# Example bread modules
+
+Ready-to-use modules for common desktop automations. Unlike the snippets in
+[`../../Examples.md`](../../Examples.md) (which teach the porting patterns),
+these are complete files you can drop in as-is.
+
+## Installing
+
+Modules in `~/.config/bread/modules/` are **auto-discovered** — copy a file in
+and reload; no `init.lua` edit needed:
+
+```sh
+cp low-battery-warning.lua ~/.config/bread/modules/
+bread reload
+```
+
+## Modules
+
+| File | What it does | Config needed |
+|------|--------------|---------------|
+| `low-battery-warning.lua` | Critical notification once when the battery runs low; resets on AC. | none |
+| `pause-media-on-headphone-unplug.lua` | Runs `playerctl pause` when a headphone/earbud device disconnects. | none (needs `playerctl`) |
+| `dock-monitors.lua` | Applies a multi-monitor layout when an external display connects, reverts when removed. | edit output names/resolutions |
+
+Each module is the standard skeleton — `bread.module{...}`, an `on_load` that
+registers subscriptions, `return M` — so they double as references for writing
+your own. See [`../../Documentation.md`](../../Documentation.md) for the full
+event list and Lua API.