Move keyboard.js to handlers folder, because it's an override of the

part of Leaflet keyboard handler.

Author: prushfor

src/mapml/keyboard.js renamed to src/mapml/handlers/keyboard.js

@@ -75,7 +75,7 @@ import { Geometry, geometry } from './features/geometry';
 import { AnnounceMovement } from './handlers/AnnounceMovement';
 import { FeatureIndex } from './handlers/FeatureIndex';
 import { Options } from './options';
-import './keyboard';
+import './handlers/keyboard';
 import {
   featureIndexOverlay,
   FeatureIndexOverlay