android: capture current keyboard height

expose a new virtual_keyboard_height function under notedeck::platform::android

which gets the current height of the virtual keyboard. We can use this
to tranlate the view out of the way

Signed-off-by: William Casarin <jb55@jb55.com>

Cargo.lock

@@ -2783,6 +2783,7 @@ dependencies = [
  "enostr",
  "hex",
  "image",
+ "jni",
  "mime_guess",
  "nostrdb",
  "poll-promise",