Reorganize Classic UI Theming part

[stevepiercy]

Closes #1645

---

📚 Documentation preview 📚: https://plone6--1831.org.readthedocs.build/classic-ui/theming/index.html

[stevepiercy]

@plone/classicui-team please review.

[stevepiercy]

First person to review this PR gets a 🍪 !

@petschki
@yurj
@MrTango
@jensens
@1letter

It has one section where I need some help to clarify it, please!

[stevepiercy]

We have to ignore the pull request preview build failure for a while. I just filed an issue with RTD at readthedocs/readthedocs.org#11912

[petschki]

I'm happy with the restructuring here. Thank you!

[petschki]

Where's my 🍪 😉

[stevepiercy]

Where's my 🍪 😉

I'll bring a batch for the next PloneConf or sprint. 😁

I need help with this TODO, as I don't have the experience or knowledge. If y'all can give me some notes, I can wordsmith something together.

https://plone6--1831.org.readthedocs.build/classic-ui/theming/index.html

[stevepiercy]

@petschki @yurj @MrTango @jensens @1letter

I need help with this TODO about choosing a theming method, as I don't have the experience or knowledge. If y'all can give me some notes or guidance, I can wordsmith something together and finish up this PR.

https://plone6--1831.org.readthedocs.build/classic-ui/theming/index.html

Thank you!

[ale-rt]

@stevepiercy what about merging master and merging this PR with the TODO?
We can add it later.

[stevepiercy]

@ale-rt we've tried that, and it doesn't work. A little bit of evidence:

• https://6.docs.plone.org/classic-ui/forms.html
• https://6.docs.plone.org/classic-ui/templates.html
• https://6.docs.plone.org/backend/annotations.html
• https://6.docs.plone.org/backend/configuration-registry.html
• https://6.docs.plone.org/backend/search.html
• https://6.docs.plone.org/backend/security.html
• https://6.docs.plone.org/backend/sending-email.html
• https://6.docs.plone.org/backend/subscribers.html
• https://6.docs.plone.org/backend/users-groups.html
• https://6.docs.plone.org/backend/vocabularies.html
• https://6.docs.plone.org/backend/workflows.html
• https://6.docs.plone.org/backend/zodb.html

There's also the embarrassment of completing only 13% of Plone 6.0 and 6.1 documentation issues at the time of Plone 6.1 release.

[stevepiercy]

@petschki @yurj @MrTango @jensens @1letter

I need help with this TODO about choosing a theming method, as I don't have the experience or knowledge. If y'all can give me some notes or guidance, I can wordsmith something together and finish up this PR.

Since I got no response, I'm inclined to refer readers to get help to make a choice in the Classic UI Community Forum topic and Discord channel.

I'll revisit this when I get some time, but it can't be merged until helpful content replaces the todo.