Add sniff to require a colon after a case instruction

A sniff and fixer for this has been written and it is part of PHP-CS-FIXER but I don't think this is currently loaded and available in Coder. What is the policy regarding installing new requirements vs writing our own sniffs?

PHP-CS-Fixer is a different system than PHPCS. Coder uses PHPCS sniffs.

Integrating or running PHP-CS-Fixer is a bit out of scope for this Coder issue, but I'm open to review approaches how we could leverage PHP-CS-Fixer as parallel system to PHPCS in Coder.

Duplicate of 📌 Can we enforce case statements ending in a : instead of a ; Active .