Install foreman for procfile and setup appdomain in gitpod (#14612)

* Install foreman for procfile and setup appdomain for csrf in gitpod

Foreman was not installed (so bin/startup would fail fast).

Additionally, the APP_DOMAIN can be fetched from the `gp` utility to
get the url for port 3000

Since the .env file is read top down - it's easier to implement
appending the corrected value than to replace it at the beginning, but
I'm completely open to redoing this via a sed command or similar to
change the variable at the top (this would be less confusing for
anyone else dealing with the file).

* Ensure command executes as a series of commands

TODO: if this works move the echo commands into the setup section

* move .env setup commands to init section

.gitpod.yml

@@ -17,7 +17,10 @@ tasks:
       redis-server &
     init: >
       cp .env_sample .env &&
+      echo "APP_DOMAIN=\"$(gp url 3000 | cut -f 3 -d /)\"" >> .env &&
+      echo 'APP_PROTOCOL="https://"' >> .env &&
       gem install solargraph &&
+      gem install foreman &&
       bin/setup
     command: >
       bin/startup