Show stickers on click

[p1gp1g]

Open stickers and play animated sticker

Fix #2668

Type of change

• Feature
• Bugfix
• Technical
• Other :

Content

Stickers can be clicked to show their content.

Motivation and context

Some stickers need to be opened to be seen (too small) or to be played (GIF) but it wasn't possible.

Screenshots / GIFs

Tests

• Send a playable sticker on a room (For instance with https://duckchi.github.io/stickerpicker/web/)
• Click on it

Tested devices

• Physical
• Emulator
• OS version(s): 9, 11

Checklist

• Changes has been tested on an Android device or Android emulator with API 21
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request includes a new file under ./changelog.d. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#changelog
• Pull request includes screenshots or videos if containing UI changes
• Pull request includes a sign off
• You've made a self review of your PR
• If you have modified the screen flow, or added new screens to the application, you have updated the test UiAllScreensSanityTest.allScreensTest()

[bmarty]

LGTM, thanks!