Make certain parts of the scoreboard sticky, relevant when having many problems/very wide scoreboard

[vmcj]

I encountered this when testing for something else. When there are many problems we don't fit in the viewport anymore (horizontal we move out of a browser window). If the viewer would scroll certain parts should stay:

• banner
• warnings (this is not a real contest), frozen status (contest frozen with 120 min remaining) etc.
• The legenda & filter button, the "generated on time"

I couldn't get the team names to become sticky as that would remove the border (https://stackoverflow.com/a/53559396).

PR mostly for discussion, after approval I'll squash this to one.

[vmcj]

The progress bar is not sticky yet.

[meisterT]

What is the difference between this and https://github.com/DOMjudge/domjudge/pull/2132?

[vmcj]

What is the difference between this and #2132?

Everything, this does something completely else. In this one I make the overview (well tried, the team page seems to have been forgotten) and make that you can scroll when having loads of problems (so the scoreboard is quite wide)

The other one tries to keep the scoreboard summary (so based on the length) sticky when scrolling. So one works on horizontal scrolling (in a sort of edgecase) the other one when having multiple sortorders or enough teams to fill more than 1 viewport.