feat(accessibility): add support for escape key handling

[tavanuka]

Resolves #512.

This PR aims to add escape key handling support for modal instances by having a global handler which programmatically closes last-most instance when the escape key is pressed.

Instead of registering a handler per instance, a global handler is registered once via JavaScript and bypasses using event handlers.

Although I am not the biggest fan of JS, I see no other way for this use-case to be solved. This solution should also mitigate any weird and inconsistent behaviours that occurred with the previous fix caused by #201 and #202.

Additionally, support for disabling escape key handling can be set globally, or per-instance.

I have extended the unit tests to ensure coverage of the newly added feature.

@chrissainty If possible, a review and potential merge would be optimal - as we use this dependency in the customer's project extensively and its requirement is better accessibility. I was assigned to implement this feature, with additional colleague tasked to do a review of my changes - as they do not wish to resort to having to compile a fork.

[tavanuka]

Workflow action requires approval to be executed.

[NeskireDK]

Clear and simple solution, that aligns perfectly with existing code. Its a thumbs up from me, ill unsubscribe the #512 in hopes that this will be merged in.
Fair warning though, I haven't got a code base handy to test it myself.

[tavanuka]

@NeskireDK Thank you. Code has been internally tested by my colleague and vibe checked in case I have done any hiccups. According to him: "LGTM"

[tavanuka]

I will add a documentation entry describing this feature. I forgot about this