docs: post-release version bump PRs

This more clearly specifies that version bumps should have a PR which is assigned to the next caretaker. It also specifies that the caretaker should include these PRs in the hand-off to the next caretaker. If anyone who notices these links missing, they should escalate to the caretaker just to make sure this step is not forgotten. This should make it less likely for a caretaker for forget to do the post-release version bump.

(cherry picked from commit de63f41)

Author: dgp1130

docs/process/release.md

@@ -151,14 +151,24 @@ using the `--githubToken` flag. You just then have to confirm the draft.
 
 ## Post-release Version Update
 
+**For each released version**:
+
 Update the package versions to reflect the *next* release version in **both**:
 1. `version` in [`package.json`](https://github.com/angular/angular-cli/blob/master/package.json#L3)
 1. `DevkitBuild*` in [`packages/schematics/angular/utility/latest-versions.ts`](https://github.com/angular/angular-cli/blob/master/packages/schematics/angular/utility/latest-versions.ts)
 
 ```sh
+git checkout -b release-bump-vXX
 git commit package.json packages/schematics/angular/utility/latest-versions.ts -m "build: bump version to vXX"
+git push -u origin release-bump-vXX
 ```
 
+Then make a PR and assign it to the next primary caretaker.
+
+Don't forget to update the Slack [#tools](https://angular-team.slack.com/archives/C46U16D4Z) channel topic and also post
+links to all the version bump PRs. If anyone else on the team notices these links missing, they should ask the caretaker
+to make sure the post-release version bump is not forgotten.
+
 ### Microsite Publishing
 
 The [microsite](https://cli.angular.io/) is the landing page for Angular CLI and