build: the input-method and virtual-keyboard protocols

zwp_input_method_v2 and zwp_virtual_keyboard_v1, vendored verbatim from
wlroots 012ca825 under proto/ and turned into imv2.[ch] and vkv1.[ch] by
wayland-scanner; only the XML is tracked, and nothing compiles them yet.
The Dockerfile gains wayland, which carries the scanner.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

LICENSES/README.md

@@ -10,4 +10,7 @@
   emoji names and keywords in `map/emoji.src` and generated
   `map/emoji.dict`, derived from Unicode's `emoji-test.txt` and CLDR's
   annotations.
+- The two protocol descriptions in `proto/` are vendored verbatim from
+  wlroots `012ca825` and carry their own MIT terms inside the XML.
+
 No repository-wide license has been declared for original strans source.