(#618) Add context-fill and stroke for use element

Rust-analyzer shows an error but it compiles and the tests all pass using my docker scripts and without. This builds off a commit before @federico fixed clippy errors, so I'm expecting that to fail in the pipeline, but when it gets merged back up to where the rest of the repo is at it should work. I tried to do it myself but ended up messing up my local repo so I'm not entirely sure how to go about that.