Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Handle videos in:
- MD preview in notes: commit, issue/MR, MR diff
- New notes in: commit, issue/MR, MR diff
- Persisted notes in: commit, issue/MR, MR diff
Signed-off-by: NRémy Coutable <remy@rymai.me>

Add max-height to prevent images from displaying larger than the provided screen size.

Also fix a failing test and add a new one.

This reverts commit 13e37a3e.

This would happen when a todo already exists, the state of the button
wouldn't update after the ajax call

Added a button into the sidebar for issues & merge requests to allow users to manually create todo items

Closes #15045

Added sidebar
Removed elements not present in design