add_support_for_new_angular_version.txt

Notes from when I added Angular 11 support

- in uirouter/angular:
 - update peer deps for angular packages, bumping each range by one
 - update angular packages manually to the lower range supported (for angular 11, set to ^10.0.0)
 - update ng-packagr manually to the lower range supported (for angular 11, set to ^10.0.0)
 - update typescript to the version required by @angular/compiler-cli
 - npx check-peer-dependencies
 - gh pr create
 - update other libs
 - update tests in test-angular-versions/
   - ./scaffold.sh 11
   - remove old tests from test-angular-versions and ../downstream_projects.json
 - update tests in test-typescript-versions/
   - ./scaffold.sh 4.5
   - (maybe) remove old tests from test-typescript-versions and ../downstream_projects.json
 - npx check-peer-dependencies
 - gh pr create
 - npm run release

- in sample-app-angular:
 - git checkout -b update-to-latest-angular
 - npx ng update @angular/core @angular/cli
 - git commit -m "chore: update to Angular 11"
 - yarn && yarn test
 - gh pr create

- in sample-app-angular-hybrid
 - npx ng update @angular/core @angular/cli
 - yarn upgrade-interactive --latest (update uirouter libs)
 - push to a branch 'upgrade-to-angular-11'

- in uirouter/angular-hybrid
 - target the sample-app branch in downstream_test.json: 
   - "https://github.com/ui-router/sample-app-angular-hybrid.git@update-to-angular-11"
 - update peer deps for angular packages, bumping each range by one
 - update angular packages manually to the lower range supported (for angular 11, set to ^10.0.0)
 - update ng-packagr manually to the lower range supported (for angular 11, set to ^10.0.0)
 - update typescript to the version required by @angular/compiler-cli
 - npx check-peer-dependencies
 - in example
  - npx ng update @angular/core @angular/cli
  - yarn upgrade-interactive --latest (update uirouter libs)
 - gh pr create
 - npm run release
 - revert downstream_projects.json and push

- in sample-app-angular-hybrid after merging
 - yarn upgrade-interactive --latest (update uirouter libs)
 - push and merge