Pre Emulator Launch Script (#247)

* Add `pre-emulator-launch-script` to `action.yml`

* Add `pre-emulator-launch-script` in `main.yml`

* Implement pre emulator launch script

* Try to use `pushd`

* print working directory

* Add `README`

* Run `npm run build`

* Fix `working-directory`

* Run `npm run build`

* Run pre emulator launch in group

* Run `npm run build`

* Update README.md

Co-authored-by: Yang <reactivecircus@gmail.com>

* Add type "pre-emulator-launch-script"

Co-authored-by: Yang <reactivecircus@gmail.com>

.github/workflows/main.yml

@@ -114,6 +114,9 @@ jobs:
         disable-animations: true
         working-directory: ./test-fixture/
         channel: canary
+        pre-emulator-launch-script: |
+          echo "Running pre emulator launch script. Printing the working directory now:"
+          pwd
         script: |
           echo $GITHUB_REPOSITORY
           adb devices