Chats

Closes #201 (closed)

Timeline

• the timeline updates the unread indicator and the message content (video, screenshot)

Starting a new chat

• allows selecting a user using the search (the default is the people the user most recently chatted with) (video)
• if the conversation with the selected user already exists, it redirects to it

The chat view

• deletion (the menu appears on message click — works the same way on mobile and desktop)
• message sequence by the same user in a 1-1 chat (screenshot)
• mobile layout (screenshot)
• the colors can be customized at Settings -> Themes -> Advanced -> Chats (screenshot)
• theme support:
  • Pleroma Dark
  • Pleroma Light
  • Bird
  • Monokai
  • Mammal
• scroll helper and new message indicator (video)
• attachments

Misc

• the "Message" button is added to the user profile card, it takes to the latest chat with the user or starts a new one