docs: update release docs to describe how to upgrade the browser policy

Author: dgp1130

docs/process/release.md

@@ -145,3 +145,24 @@ will block the next weekly release.
     accept the invite for the new package.
 
 Once Wombat accepts the invite, regular automated releases should work as expected.
+
+## Updating Browser Support
+
+Angular's browser support is defined by a [Baseline](https://web.dev/baseline) "widely available"
+date. Before a new major version is released, this should be updated to approximately the current
+date.
+
+A few weeks before a major (around feature freeze):
+
+1.  Update `baselineThreshold` in
+    [`browserslist/package.json`](/packages/angular/build/src/browserslist/package.json) to the
+    end of the most recent month.
+    - For example, if it is currently May 12th, set `baselineThreshold` to April 30th.
+    - Picking a date at the end of a month makes it easier to cross-reference Angular's support
+      with other tools (like MDN) which state Baseline support using month specificity.
+    - Commit and merge the change, no other alterations or automation is necessary in the CLI
+      repo.
+2.  Update
+    [`angular.dev` documentation](https://github.com/angular/angular/tree/main/adev/src/content/reference/versions.md#browser-support)
+    to specify the date used and link to [browsersl.ist](https://browsersl.ist) with the
+    generated configuration.