MAINT: Add copyright to the top of each file

[larsoner]

This script tools/dev/ensure_headers.py reads all .py files in our source tree and ensures that our standard license line shows up followed by a new copyright line suggested by bestpractices.dev. Only takes a few hundred milliseconds to run, and running it more than once is a no-op. Eventually we could maybe turn it into a pre-commit hook but for now we can probably just add it to our release instructions as yet another step. It provides a framework for eventually (in another PR) tackling #11605.

[larsoner]

Leaving this as draft mode just to avoid pinging pretty much the entire steering council :) @drammock feel free to take a look and see if it makes sense to you

[larsoner]

@drammock this is the one new file. Might be easiest to check out my branch and look at tools/dev/ensure_headers.py locally. GitHub is really slow with a diff across so many files

[drammock]

should we add gitpython as a new dev dependency in pyproject.toml? I'm OK with that but also OK omitting it since it's only the release manager du jour that needs it. I looked at the script on your fork as suggested, LGTM.

[cbrnr]

Shouldn't it be "Copyright by the MNE-Python contributors."?

[sappelhoff]

Shouldn't it be "Copyright by the MNE-Python contributors."?

the wording here is the one suggested here: https://www.bestpractices.dev/en/projects/7783?criteria_level=2

I'd be +1 to keep in line with their "template"

[larsoner]

Pushed to main as 5897b81