Release: migrate release process to release-it

*Authors*
- Checking and updating authors has been migrated
  to a custom script in the repo

*Changelog*
- changelogplease is no longer maintained
- generate changelog in markdown for GitHub releases
- generate changelog in HTML for blog posts
- generate contributors list in HTML for blog posts

*dist*
- clone dist repo, copy files, and commit/push
- commit tag with dist files on main branch;
  remove dist files from main branch after release

*cdn*
- clone cdn repo, copy files, and commit/push
- create versioned and unversioned copies in cdn/
- generate md5 sums and archives for Google and MSFT

*build*
- implement reproducible builds and verify release builds
  * uses the last modified date for the latest commit
  * See https://reproducible-builds.org/
- the verify workflow also ensures all files were
  properly published to the CDN and npm

*docs*
- the new release workflow is documented at build/release/README.md

*misc*
- now that we don't need the jquery-release script and
  now that we no longer need to build on Node 10, we can
  use ESM in all files in the build folder
- move dist wrappers to "wrappers" folders for easy removal
  of all built files
- limit certain workflows to the main repo (not forks)
- version in package.json has been set to beta.1 so that
  the next release will be beta.2
- release-it added the `preReleaseBase` option and we
  now always set it to `1` in the npm script. This is
  a noop for stable releases.

Fixes jquery/jquery-release#114
Closes gh-5512

dist-module/wrappers/jquery.node-module-wrapper.js

@@ -0,0 +1,5 @@
+// Node.js is able to import from a CommonJS module in an ESM one.
+import jQuery from "../../dist/jquery.js";
+
+export { jQuery, jQuery as $ };
+export default jQuery;

dist-module/wrappers/jquery.node-module-wrapper.slim.js

@@ -0,0 +1,5 @@
+// Node.js is able to import from a CommonJS module in an ESM one.
+import jQuery from "../../dist/jquery.slim.js";
+
+export { jQuery, jQuery as $ };
+export default jQuery;