WIP proposed use of {rsvg}

[jimjam-slam]

This proposes using rsvg::rsvg_svg instead of grConvert::convertPicture (as that package is no longer maintained, and rsvg uses the same library).

Unfortunately, I'm getting a runtime error that crashes R whenever I try to call rsvg_svg presently.

[jimjam-slam]

@rempsyc I've merged the 0.0.4 updates (to fix your R CMD checks) from main into feature-newflags, but for some reason after the merge lflags is no longer listed as a package export when I'm testing the new branch (regardless of whether I use the previous lflags.rda or the one generated with the new {rsvg} and {grConvert}). Not sure if I've missed something when merging the branches; I'll need to do a comparison to see why main is working and feature-newflags isn't!

[jimjam-slam]

Continued in #31