Update Docs: migrate Beta Features - Custom Mount Element

[privatemaker]

Given how minimal this is, it feels wrong it is on own page, but it seems semantically to make most sense.

I am not sure in what creative cases this is useful or what code to do it looks like- maybe because I am not a React developer? 🤔

@martinjagodic perhaps adding some example snippets and slightly more text or links to examples?

Relating to #7040

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[martinjagodic]

I agree, this should be better documented. Let me take some time for this and get back with some snippets.

[martinjagodic]

It is pretty easy: Just add id="nc-root" to any element, and the CMS will load into it. It is useful if you want to create a wrapper around the CMS, like a custom header or footer.

My suggestion for the docs:

---

For example, adding this div to admin/index.html will cause the CMS to load within it:

<div id="nc-root"></div>

[privatemaker]

Super. Thank you for clarifying. I incorporated that into the page 😄