Ability to load query from external source

[thibaultmol]

I noticed that Overpass Ultra has something pretty cool, they can load an overpass query via a github gist or any raw link:

https://wiki.openstreetmap.org/wiki/Ultra/URL_Parameters#Loading_URLs

It would be interesting if Turbo could also do this (then you could have a permanent link but that links to gist or some other place where the script can stay up to date. useful for sharing with others