Account for upcoming change in WP 5.7 / script tag use

[jrfnl]

PR WordPress/WordPress-Coding-Standards#1956 in WPCS refers to changes in WP Core which will remove the use of the <script> HTML tag in PHP code.

Any existing sniff which looks at the content of inline HTML and takes the <script> tag into account will need to be reviewed to see if it can still detect what it is looking for with the "new" way of writing this type of code.

This PR to WP Core gives some good examples of the "new" way of writing this type of code and can be used to for code samples: https://github.com/WordPress/wordpress-develop/pull/498/files

This PR shows the new functionality which will be added to Core: WordPress/wordpress-develop#591

[rebeccahum]

Related sniff in progress: #623