Merge branch 'dropdown-arrow-support' into 'master'

Dropdown arrow support

When the dropdown is open, you can scroll through the list of items with the up & down arrow keys. When an item is focused, the enter triggers the click event for that row.

Closes #14455

See merge request !3385
25 jobs for master
Status Job ID Name Coverage
  Test
passed #1004166
ruby mysql
brakeman

00:11:09

passed #1004169
ruby mysql
bundler:audit

00:12:20

passed #1004168
ruby mysql
flay

00:12:38

passed #1004167
ruby mysql
flog

00:12:08

passed #1004164
ruby mysql
rubocop

00:12:19

passed #1004165
ruby
scss-lint

00:12:51

passed #1004155
ruby mysql
spec:api

00:22:15

passed #1004172
ruby mysql
spec:api:ruby22

00:26:17

passed #1004154
ruby mysql
spec:feature

00:36:52

passed #1004170
ruby mysql
spec:feature:ruby22

00:30:35

passed #1004157
ruby mysql
spec:lib

00:24:53

passed #1004174
ruby mysql
spec:lib:ruby22

00:24:11

passed #1004156
ruby mysql
spec:models

00:21:39

passed #1004173
ruby mysql
spec:models:ruby22

00:33:12

passed #1004159
ruby mysql
spec:other

00:37:31

passed #1004176
ruby mysql
spec:other:ruby22

00:26:06

passed #1004158
ruby mysql
spec:services

00:43:11

passed #1004175
ruby mysql
spec:services:ruby22

00:38:18

passed #1004162
ruby mysql
spinach:other

00:27:46

passed #1004179
ruby mysql
spinach:other:ruby22

00:29:09

passed #1004160
ruby mysql
spinach:project:half

00:45:44

passed #1004177
ruby mysql
spinach:project:half:ruby22

00:26:20

passed #1004161
ruby mysql
spinach:project:rest

00:28:39

passed #1004178
ruby mysql
spinach:project:rest:ruby22

00:31:10

passed #1004163
ruby mysql
teaspoon

00:13:24