Hook events into Markdown render using ref.

Fix: Show correct time format on left side of messages.

Temporary change: Prevent TextFile from loading large content.
Fixes #1: File preview failing with JSON files.
Add a way to open text files in new tab.

- attachment scaling now works for all forms of attachments
- switched to grid based action bar
- added onLoad class so image proportions are "trimmed" once the image has loaded to avoid moving the view around before loading
  - this may be possible to remove at some point

- replaced many uses of `as any` with another more specific cast `as T`
- filled in missing typed for items that needed to be typed
  - new runtime code was added where necessary to satisfy the new types with comments
- added missing theme variable "sidebar-active" to the Theme variables
- forms using `react-hook-form` are now typechecked
- changed some instances of `target` into `currentTarget` while removing `as any` assertions

Fix strokes on home sidebar.
Add tooltips on servers.
Fix reply SVG direction.

Add bars + header + sidebar to channels.