Enhance and standardize local development setup

I would like to standardize our whole development environment according to best practices--above all, using DDEV and the DDEV Drupal Contrib add-on. This MR adds the essential configuration and then leverages it to add several convenience, productivity, and quality of life enhancements. ...and sneaks in some documentation updates.

To the reviewer(s): most of the command files are added by ddev/ddev-drupal-contrib. Unfortunately, there doesn't seem to be a package management solution for DDEV add-ons akin to Composer or Yarn. But the files are unaltered, so you can trust them just as much as you would any other third party code from a trusted source--if you trust me, of course 😉. The custom commands I wrote are namespaced:

$ ddev | grep jqb:
  jqb:build-js         Build the JSON:API Query Builder React app. (shell web container command)
  jqb:init             Initialize the JSON:API Query Builder development environment. (shell host container command)
  jqb:install-site     Install Drupal and enable the JSON:API Query Builder module. (shell web container command)
  jqb:release          Prepare a release artifact for the JSON:API Query Builder module. (shell web container command)

These automate most of the major operations needed to set up and test and contribute to the module, and they remove all host dependencies (except for DDEV itself) by moving the operations inside the container. All-in-all, this should make it much easier to onboard new contributors and work with the codebase on a day-to-day basis.