Native Shift Left goodies

[blaggacao]

This issue aims to replace #16 with a more concise and well defined generic use case instead of calling for particular tooling, see https://github.com/numtide/devshell/issues/16#issuecomment-699684793.

Shift left is a strategy to move CI and CD components into the — figuratively — "airplane mode".

This typically involves a range of things like:

• Code formatting
• Code linting
• Code generators
• Integration testing
• Deploy spec overlay rendering
• Even artifact generation (and pushing once off the plane)

In my interpretation, this approach mainly avoids the ownership mismatch of central tooling.

Typical tools involed in the solution are:

• formatting → $EDITOR hooks + .editorconfig
• linting → pre-push — cave: not pre-commit — hooks.
• code generators → pre-push or task runner
• e2e, etc. → task runner (e.g. make or just)

[blaggacao]

I think the only remaining useful consideration out of this would be to provide user defined sub-menus, like ci-menu where all checks are amassed.