Description of phpCAS import into Moodle

Last release can be found at https://github.com/apereo/phpCAS/releases

NOTICE:
 * Before running composer command, make sure you have the composer version updated.
 * Composer version 2.2.4 2022-01-08 12:30:42

STEPS:
 * Make sure you're using the lowest supported PHP version for the given release (e.g. PHP 7.4 for Moodle 4.1)
 * Create a temporary folder outside your Moodle installation
 * Execute 'composer require apereo/phpcas:VERSION'
 * Check any new libraries that have been added and make sure they do not exist in Moodle already.
 * Remove the old 'vendor' directory in auth/cas/CAS/
 * Copy contents of 'vendor' directory
 * Create a commit with only the library changes.
   - Note: Make sure to check the list of unversioned files and add any new files to the staging area.
 * Update auth/cas/thirdpartylibs.xml
 * Apply the modifications described in the CHANGES section
 * Create another commit with the previous two steps of changes

CHANGES:
 * Remove all the hidden folders and files in vendor/apereo/phpcas/ (find . -name ".*"):
  - .codecov.yml
  - .gitattributes
  - .github
