seat: implement input methods

wire/zwp_input_method_keyboard_grab_v2.txt

@@ -0,0 +1,29 @@
+request release {
+
+}
+
+event keymap {
+    format: u32,
+    fd: fd,
+    size: u32,
+}
+
+event key {
+    serial: u32,
+    time: u32,
+    key: u32,
+    state: u32,
+}
+
+event modifiers {
+    serial: u32,
+    mods_depressed: u32,
+    mods_latched: u32,
+    mods_locked: u32,
+    group: u32,
+}
+
+event repeat_info {
+    rate: i32,
+    delay: i32,
+}