Cross-platform selection prevention in lobby and header

[johndoknjas]

On a PC, the user isn't allowed to select certain things from the header and areas of the lobby. This PR extends that to include other platforms, like phones. Now something like the following (screenshot from my iphone) won't be possible:

[ornicar]

Are you sure they're all necessary? According to MDN only safari needs it

[johndoknjas]

@ornicar That link only shows an example for Safari, but I'm not sure if they explicitly said that's the only browser that needs it (edit: the table says it is for current versions). It's probably the most important one in any case, though I saw the others mentioned in some SO answers, such as this slightly dated one. They're mainly for supporting older browsers - e.g., -ms-user-select is for IE and non-chromium versions of Edge. Although when highlighting over -ms-user-select in vscode it says it's non-standard and to avoid using it...

[ornicar]

You'll find our browser support table here, Edge pre-chromium is not supported.