2.22: Get queue endpoint

Added

• Integration tests via GHA (non-user endpoints)
• Unit tests for new releases, passing limit parameter with minimum and maximum values of 1 and 50
• Unit tests for categories, omitting country code to test global releases
• Added CODE_OF_CONDUCT.md

Fixed

• Incorrect category_id input for test_category
• Assertion value for test_categories_limit_low and test_categories_limit_high
• Pin Github Actions Runner to Ubuntu 20 for Py27
• Fixed potential error where found variable in test_artist_related_artists is undefined if for loop never evaluates to true
• Fixed false positive test test_new_releases which looks up the wrong property of the JSON response object and always evaluates to true