feat: get contribute section from README

[RichardLitt]

This should grab the Contribute heading and section from the README, if it exists, and use it instead of the fixtures Contribute.

We want to do the same with the license, later - if there is no license file, but there's a section in the README, add the license. Likewise for vice versa.

Related to #12.

[wooorm]

@RichardLitt So you’re saying that, if there’s no CONTRIBUTING.md, we should grab the contents of the section if it’s in the README.md, and place it in CONTRIBUTING.md?

...and the same for LICENSE in the future?

Is there an example of a thing I could use as inspiration, that adds a file if it isn’t already there?

[RichardLitt]

Yep! That's exactly what I am saying. We can probably grab the SPDX and fill in the license, too.

Build a space does this already, adding a file if it isn't there. Look for community checkers - the code should be relatively straightforward to read.

[wooorm]

I don’t have access to that, so I couldn’t try it out, but GH-57 should do the trick!

[RichardLitt]

What don't you have access to?

[wooorm]

Oh sorry this comment went to the wrong issue/pr, it was about the one you mentioned with a Contribute section but no CONTRIBUTE.md file. Never mind!

[RichardLitt]

This is superseded by #57. Closing.

[wooorm]

Should the branch be deleted?