infra: setup staging environment

[Shehryar21]

Brief description. What is this change?

Create Developer Staging Environment

Implementation description. How did you make this change?

• Created a new staging site on firebase communityfridgekw-staging.web.app
• Created a new staging app on Heroku for backend server and db
• Created a new staging branch on github
• Updated github actions and secrets accordingly
• With these new changes, main is the production branch and once this PR is merged to main, new PRs will be merged to the staging branch after.

Steps to test

1. Verify main production site https://communityfridgekw.web.app/ works fine
2. Verify staging site https://communityfridgekw-staging.web.app/ works fine. This wont work for now, but once something is merged on to staging branch, it will work. For now just test the preview URL.
3. Verify the backend and db for production and staging is different
4. Verify Preview URLs are working fine and is working on the staging backend

Checklist

• My PR name is descriptive and in imperative tense
• My commit messages follow conventional commits and are descriptive. My commits are atomic and trivial commits are squashed or fixup'd into non-trivial commits
• I have run the appropriate linter(s)
• I have requested a review from the PL, as well as other devs who have background knowledge on this PR or who will be building on top of this PR
• The appropriate tests if necessary have been written

[github-actions]

Visit the preview URL for this PR (updated for commit a4bbb4f):

https://communityfridgekw-staging--pr91-setup-staging-enviro-68s2z6n9.web.app

_{(expires Mon, 24 Jan 2022 19:14:08 GMT)}

_{🔥 via Firebase Hosting GitHub Action 🌎}