fix: add and remove inert attributes to allow browser proper focus management for modals

[pwntr]

Addresses #41005 to get rid of the aria-hidden not applied warnings logged in the browser console.

Example warning message:

(index):1 Blocked aria-hidden on an element because its descendant retained focus. The focus must not be hidden from assistive technology users. Avoid using aria-hidden on a focused element or its ancestor. Consider using the inert attribute instead, which will also prevent focus. For more 
details, see the aria-hidden section of the WAI-ARIA specification at https://w3c.github.io/aria/#aria-hidden.
Element with focus: <div.modal fade#myModal>
Ancestor with aria-hidden: <div.modal fade#myModal> <div class=​"modal fade" id=​"myModal" tabindex=​"-1" aria-labelledby=​"myModalLabel" style=​"display:​ block;​" aria-hidden=​"true">​…​</div>

EDIT: added explicit tests for this inert attribute fix

Description

added inert attribute to the modal on hide, remove it on show

Motivation & Context

#41005

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Refactoring (non-breaking change)
• Breaking change (fix or feature that would change existing functionality)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project (using npm run lint)
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Live previews

Related issues

#41005