Improve text readability

[Jipok]

For two years I did not know that you can press r during spectating and unfollow player. I always disconnected and connected again. :) Perhaps the screenshot is hard to understand. But chat is very difficult to read now. And the description under the minimap is not at all noticeable.

I think this will greatly increase usability:

1. Increasing fonts (under dpi)
2. Adding a background to the text. Now it seems a little bit, but this is not enough.
3. Good background when h is pressed. But for some reason, the order of the text there is upside down, which is confusing. And also this key is not specified in the control settings.
4. It is also worth adding information about additional actions (for example, r - unfollow) in the control settings menu

[Jipok]

Good font rendering example: Teeworlds game. Client from DDNet.

5. There is also a good chat implementation. Server messages, regular and in team chat are different in color.

6. Messages in which there is your nickname change color. Pale red in the screenshot.

7. When you press a special key or start writing a message, the chat unfolds. Second screenshot.

8. There is also auto-completion of nicknames on the tab. Shift-tab allows you to circulate in the opposite direction

[yvt]

1. Increasing fonts (under dpi)

It's actually in the (abandoned) v0.2.0 branch (https://github.com/yvt/openspades/pull/838/commits/e0a93c801b27bb0062f93c2a8dcf07ff40da3efd) but hasn't been merged into master yet.

8. There is also auto-completion of nicknames on the tab. Shift-tab allows you to circulate in the opposite direction

Duplicate of #800