revise contributing docs

[a-frantz]

CONTRIBUTING.md has some legal stuff and not much of practical use. style-guide.md can probably be deleted in favor of just relying on sprocket lint passing. best-practices.md needs some tweaks.

[Gyan-max]

Hi @a-frantz,

I'm interested in working on this issue. I just want to confirm that since there was a recent update to CONTRIBUTING.md in the St.Jude rust labs repository so are you expecting similar changes for CONTRIBUTING.md here as well or if you have different expectations? I’d also like to confirm if style-guide.md should be fully removed in favor of sprocket lint or if any parts should be retained.