[Python] Use Fantomas formatting and check CI

[dbrattli]

So this PR might be a bit controversial with Fable 😬 but I think it's mostly a good thing with a common code style when we have many contributors. So starting with Python related code we will now enforce the formatting based on the latest Fantomas 4.6 (set as a dotnet tool) and the rules set in .editorconfig. I'm pretty agnostic to what the rules should be as long as we have a set of common rules. The current .editorconfig tries to match the current code style, but please make PR's to modify if to the Fable style.

This PR will only enforce the formatting of src/Fable.Transforms/Python but we should consider adding this to the rest of the code base as well.

To format the Python code, you will need to run:

> dotnet tool restore
> dotnet fantomas src/Fable.Transforms/Python

Fantomas is added to GitHub actions so if the Python related code is not formatted according to the rules, the build will fail. Please chime in if you do not want this kind of restrictions in Fable (even if only applied to the Python specific code) @alfonsogarciacaro @ncave

[ncave]

@dbrattli Some of the code base in Fable comes from dotnet/fsharp where there isn't any formatting, not even EOL white-space removal. So yes, IMO it would be preferable if we keep the original formatting and not enforce Fantomas on everything.

[dbrattli]

@ncave It's possible to ignore parts of the code-base using .fantomasignore, so copied / auto-generated code can be ignored from formatting. https://github.com/fsprojects/fantomas/blob/master/docs/Documentation.md#ignore-files-fantomasignore

[alfonsogarciacaro]

Fantomas has removed the comment here.

[dbrattli]

Yes, I've seen this happen a couple of times. Added issue at: fsprojects/fantomas#2027

[alfonsogarciacaro]

Yes, I've been thinking about adding Fantomas many times, but at the end I discarded by issues like the one pointed out by @ncave. Particularly right now it can make keeping main in beyond in sync more difficult, so I would postpone the decision at least until beyond replaces main. It should be fine to apply Fantomas to Fable.Transforms/Python though.

[dbrattli]

Ok, thanks for the comments. It makes sense to wait with this until after beyond merges with main. I'll still add this for Python to test if it can work, but will remove the CI hook if it becomes to annoying for the rest of you.