Update CONTRIBUTING.md with commit quality expectations

We should update CONTRIBUTING.md with a section that explains our expectations towards commit message quality and what should constitute a commit.

For example:

• You should write a good commit message for every commit. Not just maybe it'll work now.
• You should not be committing linting fixes because the build failed, just use a git hook and lint on pre-commit! There is info on how to do this in the wiki. Refer to it.
• You should not commit tiny changes at a high frequency. Commit a meaningful amount of work at a time.

This needs to be done on all three of our major projects - site, bot, and seasonalbot.

See https://github.com/python-discord/site/issues/157 and https://github.com/python-discord/seasonalbot/issues/84

[sco1]

Another nice addition would be which logging level to use for various things. Our current guidance (from March 2018) is the following:

TRACE: Use this for tracing every step of a complex process. That way we can see which step of the process failed. Err on the side of verbose. INFO: Something completely ordinary happened. Like a cog loading during startup. DEBUG: Someone is interacting with the application, and the application is behaving as expected. WARNING: Someone is interacting with the application in an unexpected way or the application is responding in an unexpected way, but without causing an error. ERROR: An error that affects the specific part that is being interacted with CRITICAL: An error that affects the whole application.

[sco1]

@GhostofGoes I haven’t yet. It’s been on my list of things to investigate for my personal & work stuff but I haven’t gotten to it.