[BBT-112] Prevent users from editing the preview

Description

Completes BBT-112 - This PR adds the inert attribute to the div that surrounds the blocks preview. This means all user interactions (input, focus, hover etc.) on the element and its children aren't registered so the user can't edit the blocks in the preview.

The only concern for this approach is that it also removes the preview from the accessibility tree, but I don't think this is an issue as I don't think visually impaired users can use the preview anyway and they shouldn't be able to tab through the blocks in the preview.

Change Log

Added inert attribute to div surrounding the blocks preview.

Steps to test

Check you can't interact with the block preview
Check other features still work as expected

Screenshots/Videos

https://github.com/bigbite/themer/assets/45216035/5ec3531c-69e1-4637-8a4d-847182eea4a6

Checklist:

[X] My code follows the style guidelines of this project
[X] I have performed a self-review of my own code
[X] I have commented my code, particularly in hard-to-understand areas
[X] I have made corresponding changes to the documentation
[X] My changes generate no new warnings
[X] Any dependent changes have been merged and published in downstream modules

bigbite / themer