Get more attention from reader since we're recommending they stop
reading at this point.

Following the discussion here: https://chat.civicrm.org/civicrm/pl/cfon7833xbyxpcjjcpqs1qqqja

added spaces so the last code block gets recognised as code

Added documentation on Michael McAndrews docker container.

Re-arrange CI doc as per some comments from Tim and link to other docs on test suites rather than replicating

In keeping with the discussions about JIRA, Gitlab, and issue management
(e.g.  https://lab.civicrm.org/infrastructure/ops/issues/817), this change
would revise the "Review Standards".  Instead of specifically requiring
*a JIRA issue* for every PR, it requires *a public explanation* (which can be
provided by JIRA, Gitlab, etc).

Note: This change tries to be the smallest reasonable alteration to the
review criteria that accomodates Gitlab.  However, perhaps we could make it
better -- e.g.  by providing examples of good and bad explanations?

Related: https://github.com/civicrm/civicrm-core/blob/master/.github/PULL_REQUEST_TEMPLATE.md

A person is not a PHP script.

Minor formatting issues, remove stray backslashes

The purpose of the intro paragraph is to prep the reader to see several
different test types/tools.  So it...  should probably use the word "test"
somewhere.