docs(angular test app): include instructions for updating nightly build (#28948)

Issue number: None

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## What is the current behavior?
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People adding a new Angular test app don't know they need to update the
Stencil nightly build.

## What is the new behavior?
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this PR. -->

- Documentation exists for adding a new Angular version to the Stencil
nightly build when creating a new Angular test app..

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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## Other information

This is related to #28945

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Co-authored-by: Maria Hutt <[email protected]>

Author: mapsandapps

packages/angular/test/README.md

@@ -113,4 +113,6 @@ Note: You may encounter some other peer dependency issues not covered by the Ang
 7. Open `./github/workflows/build.yml` and find the `test-angular-e2e` job.
 8. Find the `apps` field under `matrix`.
 9. Add "ng14" to the `apps` field.
-10. Commit these changes and push.
+10. Open `./github/workflows/stencil-nightly.yml` and find the `test-angular-e2e` job.
+11. Repeat steps 8 and 9.
+12. Commit these changes and push.