Overhaul contributing documentation for Plone 6

[stevepiercy]

Now that we have Plone core contributing documentation, I've simplified and modernized the contributing documentation.

See plone/documentation#1278.

• Closes Replace Netlify preview build command with 'tox -e docs' and remove Makefile #473
• Closes Update contribution docs #357

After merging, then merge plone/documentation#1684.

[mister-roboto]

@stevepiercy thanks for creating this Pull Request and helping to improve Plone!

TL;DR: Finish pushing changes, pass all other checks, then paste a comment:

@jenkins-plone-org please run jobs

To ensure that these changes do not break other parts of Plone, the Plone test suite matrix needs to pass, but it takes 30-60 min. Other CI checks are usually much faster and the Plone Jenkins resources are limited, so when done pushing changes and all other checks pass either start all Jenkins PR jobs yourself, or simply add the comment above in this PR to start all the jobs automatically.

Happy hacking!

[stevepiercy]

@jenkins-plone-org please run jobs

[stevepiercy]

I have no clue as to why Jenkins fails for Plone 6.0/Python 3.11 but not for Plone 6.0/Python 3.8. Help!

[ksuess]

I appreciate your overhaul. Just minor suggestions to content that was already there before this PR.

[jensens]

thanks! Minor things see comments.

[stevepiercy]

@jenkins-plone-org please run jobs

[stevepiercy]

Changes made, and I excluded GNU make as a requirement here since this project uses tox instead.

It would be nice to use one of make or tox for all of Plone, don't you think?

[ksuess]

It would be nice to use one of make or tox for all of Plone, don't you think?

Yes, a switch to make would be consistent. Definitly.

[stevepiercy]

It would be nice to use one of make or tox for all of Plone, don't you think?

Yes, a switch to make would be consistent. Definitly.

See https://community.plone.org/t/tools-for-development-gnu-make-tox-or/19708