Add ability to rescale UI

[overvolting]

The game text doesn't seem to scale with resolution.
People playing on high end monitors can't read anything.

[DolceTriade]

Hm, I think it might be necessary to create a new font measurement...

[overvolting]

If you check quake 3, I believe their fonts all scaled perfectly no matter what resolution.

[Kangz]

Yes, everything was based off a 640x480 virtual screen in q3 but librocket has fixed size fonts, for now.

@DolceTriade is there a CSS property that could help here, I can't seem to think of any :/

[overvolting]

I would call this an accessibility type.

[DolceTriade]

@Kangz Not sure, that's why I think I might need to add one.

[Veyrdite]

Renaming the issue to the broader feature. Having a slider in the UI config for this would be useful.

I think @DolceTriade mentioned something about a scalable unit (or I dream't it, I've been around too long to remember).

[DolceTriade]

I just mentioned it above in the same issue :p

#558 (comment)

Hm, I think it might be necessary to create a new font measurement...

[slipher]

@illwieckz reworked the UI to make everything based on em units instead of px, so it scales to higher resolutions.