Add unit tests for is_javascript_script_tag function

The `html-api/auto-escape-javascript-json` branch adds some new methods: `is_javascript_script_tag` and `is_json_script_tag`.

They're well documented referencing the HTML standard.

Create a PR against that branch to add unit tests for these two new methods.

The unit tests should be in a new test file and class:

`tests/phpunit/tests/html-api/wpHtmlTagProcessorScriptTag.php`