Use starters for App Hosting init (#181)

* Add package manager choices to the NPX `@apphosting/create` script, if `npm|yarn|pnpm init|create @apphosting` is used don't prompt—use the package manager from the command
* Allow for interactive directory picking
* Wire up create-next-on-firebase so `npm init next-on-firebase` works appropriately
* Download the starters based off the chosen framework
* Add `@types/express` to the Angular starter
* READMEs for the starters
* Drop Node 16 from the tests as we're having engine issues & no longer support v16

Author: jamesdaniels

.github/workflows/test.yml

@@ -57,7 +57,7 @@ jobs:
     needs: build
     strategy:
       matrix:
-        node: [16, 18, 20]
+        node: [18, 20]
       fail-fast: false
     name: Test Node ${{ matrix.node }}
     steps: