Allow uploading of SVG files to the wiki

[GunChleoc]

I have uploaded some flowcharts to https://wl.widelands.org/wiki/GitPrimer/

I had to use PNG but would prefer SVG, because it will give us better quality and save on server space + bandwidth.

[kaputtnik (franku)]

I have tried to gather some information about svg files and it looks to me that allowing svg files in the wiki can be dangerous. The main reason is: svg are xml files and can be manipulated by javascript in the same manner as a normal html document. More over svg files are allowed to contain script in it self.

This are mainly the reasons why djngo doesn't support it: https://code.djangoproject.com/ticket/14092

Why wordpress doesn't allow uplading svg files, with scripting example
https://bjornjohansen.no/svg-in-wordpress

So if we really want this, uploading svg files should only be allowed for trusted users (e.g. admins), imho.

[GunChleoc (gunchleoc)]

Let's scrap this idea then - we won't want to have to deal with potential JavaScript here.