feat(chips): add keyboard interaction. (#2046)

Add basic focus/keyboard support for chips.

 - Up/down arrows navigate chips.
 - Clicking a chip properly focuses it for subsequent keyboard
   navigation.
 - More demos.

Confirmed AoT compatibility.

References #120.

test/karma.config.ts

@@ -16,7 +16,7 @@ export function config(config) {
       require('karma-browserstack-launcher'),
       require('karma-sauce-launcher'),
       require('karma-chrome-launcher'),
-      require('karma-firefox-launcher'),
+      require('karma-firefox-launcher')
     ],
     files: [
       {pattern: 'dist/vendor/core-js/client/core.js', included: true, watched: false},