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>

.gitignore

@@ -1,5 +1,9 @@
 /*.o
 /strans
+/imv2.c
+/imv2.h
+/vkv1.c
+/vkv1.h
 /tests/*.o
 /tests/unit_test
 /tests/stress_test