Prevent triggering `hideSearchWords` when closing the modal

[stsewd]

Two things:

• The scope of the event needs to be narrowed down (from document to just the modal).
• We need to call stopPropagation so the event isn't triggered for the document object.

Closes https://github.com/readthedocs/readthedocs-sphinx-search/pull/103

[stsewd]

Docs should pass after https://github.com/readthedocs/readthedocs-sphinx-search/pull/105 is merged, and you should be able to test this at https://readthedocs-sphinx-search--104.org.readthedocs.build/en/104/index.html?highlight=sphinx&rtd_search=press%20escape

[mgeier]

Could someone please rebase to check if it works now?

[stsewd]

This can be tested at https://readthedocs-sphinx-search--104.org.readthedocs.build/en/104/index.html?highlight=sphinx&rtd_search=press%20escape, but there is this small problem https://github.com/readthedocs/readthedocs-sphinx-search/pull/104#discussion_r821045935