Add Pluto filtering

[gdalle]

Hey there! Since my package PlutoProfile.jl duplicates some code from here, I was wondering if you'd welcome a PR with the @plutoprofview macro? All it does is filter the flame graph to remove the Pluto boilerplate at the top, hopefully centering it on what we actually want to see.

[pfitzseb]

Sure.

Note that this package doesn't use FlameGraphs anymore, so tree pruning is probably going to be a bit of an effort to implement. I think it's going to be unnecessary to add a new entrypoint for this though; we can add a bunch of pruning cutoffs for VS Code/Pluto/REPL etc and things should work our fine in most cases.