fix: LaTeX: Allow to pass imports

[LecrisUT]

trafficstars

Probably not the proper way to do it

Closes #978

[LecrisUT]

One thing missing here could be to extend this beyond the LaTeX environment so that the html builder also renders correctly. Thing is this imports does not seem to be used in the non-template renderer, and I'm not sure if the html backend goes through LaTeX-like parsing.