Update documentation and codesamples for upload field, multiurl picker and richtext mce

[greystate]

📋 Description

Update main pages for UploadField, MultiUrlPicker and RichText TinyMCE property editors, for versions 15 and 16.

📎 Related Issues (if applicable)

Fixes #7270

✅ Contributor Checklist

I've followed the Umbraco Documentation Style Guide and can confirm that:

• Code blocks are correctly formatted.
• Sentences are short and clear (preferably under 25 words).
• Passive voice and first-person language (“we”, “I”) are avoided.
• Relevant pages are linked.
• All links work and point to the correct resources.
• Screenshots or diagrams are included if useful.
• Any code examples or instructions have been tested.
• Typos, broken links, and broken images are fixed.

Product & Version (if relevant)

This applies to version 15 and 16

📚 Helpful Resources

• 🧾 Umbraco Contribution Guidelines
• ✍️ Umbraco Documentation Style Guide

[mikecp]

Great update @greystate !

I just left a few minor comments 😉

Cheers!

[greystate]

I've pushed changes for all but one of your suggestions @mikecp – I'll just create the new screenshot and add that as well.

Thanks ✋

/Chriztian

[AndyButland]

All looks very good and correct to me, thanks very much @greystate and @mikecp.

Only think I'd note is that we'd want these changes copied to the 17 folder. Maybe one of you could do that or @eshanrnh will when she reviews, but just want to make sure it's not forgotten.

[eshanrnh]

The PR looks great. Just a minor suggestion to format the intro block.

@AndyButland I will copy the changes over to v17. No problem :)