* Update pull request template

* Changes as requested

* Link to https://developers.mattermost.com/contribute/server/developer-workflow/#running-only-specific-server-unit-tests

* Move PR and issue template to .github

* Update per feedback

See https://community.mattermost.com/core/pl/1ikmqhzw1ffsfepzyb4575bkih

* Changes as requested

* Remove checklist