build: tweak the release instructions

Makefile

@@ -222,11 +222,11 @@ check_kits:				## Check that dist/* are well-formed.
 	python -m twine check dist/*
 	@echo $$(ls -1 dist | wc -l) distribution kits
 
-tag:					## Make a git tag with the version number.
+tag:					#: Make a git tag with the version number (see howto.txt).
 	git tag -s -m "Version $$(python setup.py --version)" $$(python setup.py --version)
 	git push --follow-tags
 
-bump_version:				## Edit sources to bump the version after a release.
+bump_version:				#: Edit sources to bump the version after a release (see howto.txt).
 	git switch -c nedbat/bump-version
 	python igor.py bump_version
 	git commit -a -m "build: bump version"

howto.txt

@@ -39,6 +39,7 @@
     - merge to master
     - git push
 - Start the kits:
+    - opvars github
     - Trigger the kit GitHub Action
         $ make build_kits
 - Build and publish docs:
@@ -71,12 +72,11 @@
 - Update readthedocs
     - @ https://readthedocs.org/projects/coverage/versions/
         - find the latest tag in the inactive list, edit it, make it active.
-            - readthedocs won't find the tag until a commit is made on master.
         - keep just the latest version of each x.y release, make the rest active but hidden.
             - pre-releases should be hidden
     - IF NOT PRE-RELEASE:
         - @ https://readthedocs.org/dashboard/coverage/advanced/
-            - change the default and latest versions to the new version
+            - change the "default version" to the new version
         - @ https://readthedocs.org/projects/coverage/builds/
             - manually build "latest"
             - wait for the new tag build to finish successfully.