Fix encoded characters in term labels in Instant Results

[JakePT]

Description of the Change

The data for taxonomy term aggregations is send to Elasticsearch as encoded JSON, like this:

'{\"term_id\":236,\"slug\":\"blue\",\"name\":\"Blue\",\"parent\":0,\"term_taxonomy_id\":236,\"term_order\":0}'

This causes some characters, such as ampersands, inside the name field to be encoded as HTML entities. This means that when terms are displayed as facet options in Instant Results these characters are displayed in their encoded form.

This fix uses the (tiny) @wordpress/html-entities package to decode these entities.

Closes #3097

How to test the Change

Create a term that includes an & character and assign it to a post. Add the term's taxonomy as a facet to Instant Results and search for the post. The & should appear as expected in the list of facet options, and not as &. The character should also appear correct in the active filter 'chip' when the term is applied as a filter.

Changelog Entry

Fixed - An issue where some characters in taxonomy terms would appear encoded when displayed in Instant Results.

Credits

Props @JakePT

Checklist:

• I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.