Add a lint for `strpos` !== false to use str_contains

[spacedmonkey]

Is your feature request related to a problem?

Describe the solution you'd like

Add a lint for strpos !== false to use ! str_contains and the opposite. See WordPress/wordpress-develop@9e9887d. str_contains is a php 8.0 function but a polyfill was added in core in WP 5.9. WordPress/wordpress-develop@3cc8f12

Additional context (optional)

[jrfnl]

Note: This type of sniff should be created in the Modernize standard in PHPCSExtra and then used by WPCS.