Add execution platform compatibility section for element templates

[jarekdanielak]

Description

Related to https://github.com/camunda/product-hub/issues/2368

With Element Templates Runtime Versions feature integrated in both Desktop and Web Modelers, we should add it to the documentation.

Element template JSON schema has a new engines property which can be used to specify template's compatibility with different execution platforms.

When should this change go live?

• This is a bug fix, security concern, or something that needs urgent release support.
• This is already available but undocumented and should be released within a week.
• This on a specific schedule and the assignee will coordinate a release with the DevEx team. (apply hold label or convert to draft PR)
• This is part of a scheduled alpha or minor. (apply alpha or minor label)
• There is no urgency with this change and can be released at any time.

PR Checklist

• My changes are for an already released minor and are in /versioned_docs directory.
• My changes are for the next minor and are in /docs directory (aka /next/).

• My changes require an Engineering review, and I've assigned the Engineering DRI or delegate.
• My changes require a technical writer review, and I've assigned @camunda/tech-writers as a reviewer.

[github-actions]

👋 🤖 ✅ Looks like the changes were ported across versions, nice job! 🎉

You can read more about the versioning within our docs in our documentation guidelines.

[christinaausley]

Is this still in draft because you have additional changes you would like to make? I see this is flagged for alpha-2, which went out last week. Do you require urgent review and release?

[jarekdanielak]

Fixed the target release label, sorry about that!

[jarekdanielak]

Thanks @barmac, suggestions applied.

Backported to 8.6 and 8.5.

[barmac]

One comment still to address, but it looks good to me. @christinaausley would you say this makes sense to you? I might be biased as I was close to the implementation.