docs: bump schematics-for-libraries example peer deps to v22

The my-lib schematics-for-libraries example still declared `^21.0.0`
peerDependencies, the only adev example left on the previous major. Bumps
`@angular/common`/`@angular/core` to `^22.0.0`, matching the current major
and this file's stable-`^N.0.0` bump pattern.

Also adds this example's package.json to .prettierignore: it contains
`// #docregion` markers consumed by the schematics-for-libraries guide, and
Prettier's json-stringify parser (used for any package.json) rejects those as
invalid JSON. Editing the file surfaced this pre-existing incompatibility in
the format check.

.prettierignore

@@ -38,6 +38,10 @@ adev/src/content/aria/**/*.json
 adev/src/content/cli/**/*.json
 adev/src/content/cdk/**/*.json
 
+# Example package.json containing docregion (`// #docregion`) markers, which are
+# not valid JSON and cannot be processed by Prettier's json-stringify parser.
+adev/src/content/examples/schematics-for-libraries/projects/my-lib/package.json
+
 # Antigravity rules
 .agent/rules/agents.md
 

adev/src/content/examples/schematics-for-libraries/projects/my-lib/package.json

@@ -9,8 +9,8 @@
     "postbuild": "copyfiles schematics/*/schema.json schematics/*/files/** schematics/collection.json ../../dist/my-lib/"
   },
   "peerDependencies": {
-    "@angular/common": "^21.0.0",
-    "@angular/core": "^21.0.0"
+    "@angular/common": "^22.0.0",
+    "@angular/core": "^22.0.0"
   },
 // #docregion collection
   "schematics": "./schematics/collection.json",