Also:

- Clarify that PRs don't need to have associated tickets
- Clean up some language here and there

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

Missing ; and .

Three changes here:
 * Sort criteria in the same order across all three templates.
 * For meta-instructions, use the Markdown/HTML comment notation.
 * For `r-run`, we really don't want boilerplate. Remove the boilerplate.

The DEL workflow produces more readable output.

This makes it easier to find for people who come to the page just
looking for this one thing, which should be a common use-case of this
content.

There was confusion in some docs about `r-user` vs `r-users`. Standardize on `r-user`.

The name `r-technical` was bit more verbose than all the other abbreviations. `r-tech` looks like it'll fit better.

style guide ref:
https://docs.civicrm.org/dev/en/latest/documentation/style-guide/#hackable-urls

I'd like to be able to merge the general, incremental improvements for the
"Testing" section, but these two new pages aren't yet written.  Comment them
out.

There are multiple tools for testing in JS. We'll want separate pages for each.

 * Simplify titles under "Common standards". (Use a noun-phrase instead of an imperative statement.)
 * Combine `r-ext`, `r-core` into r-technical. Add more details. Reference `#gotchas`.
 * Rename `r-read` to `r-code`
 * Rename `rg-schema` to `rg-upgrade`. Add more details.

To see actual examples of the coding style, you need to skim multiple blurbs
and click multiple links, and the eventual page shows very isolated
examples.

This revision adds a brief example so that a new contributor can get a
general sense of the layout immediately.

(Note: It's not possible for a brief example to show every edge-case, and we
shouldn't try -- that's why the commit also emphasizes the link into the
relevant examples from d.o docs.)

Replace 'Wordpress' with 'WordPress' to use correct camel casing according to the WordPress Wordmark and Trademark