Composer: implement CS menu and extra commands

[jrfnl]

Context

• CI/Composer scripts improvement

Summary

This PR can be summarized in the following changelog entry:

• CI/Composer scripts improvement

Relevant technical choices:

This adds a number of extra CS-related Composer scripts and handler functions.

This:

• Uses the same menu as is already in use in the Free, Premium and several other plugins for predictability.
• Where necessary, adjusts existing Composer scripts to, again, be in line with what is already in use in Free and Premium.

This also adds the ability to run CS with a Threshold. As the codebase is currently clean, this ability is not activated for CI for the time being, though it is likely that it will be activated once YoastCS 3.0 will be used.

Note: this change does mean that, in contrast to before, running check-cs will now return only errors. While this is new for this package, it is in line with the expected behaviour for the script as used in other packages.

Test instructions

Test instructions for the acceptance test before the PR gets merged

This PR can be acceptance tested by following these steps:

• Run composer check-cs-thresholds or any of the other new scripts to verify that things work as expected

[coveralls]

Pull Request Test Coverage Report for Build 7228937204

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 50.203%

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Totals
Change from base Build 7180042685:	0.0%
Covered Lines:	1236
Relevant Lines:	2462

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💛 - Coveralls