chore: Add nightly build workflow

[lahirumaramba]

• Add nightly build workflow.

[hiranya911]

Thanks. LGTM with a suggestion for future improvement.

[hiranya911]

I've been thinking if we should try and reduce the duplication here. Something like:

- name: Generate email text
  if: failure() || cancelled()
  run: ./.github/scripts/generate_email.sh
  env:
    WORKFLOW_CANCELLED: ${{ cancelled() }}
    WORKFLOW_FAILED: ${{ failure() }}

- name: Send email
  uses: firebase/firebase-admin-node/.github/actions/send-email@master
  ...

No need to do this urgently. But something to think about.

[lahirumaramba]

Good call!
I will use one of the other repos to test this out first. Thanks!

[hiranya911]

I've changed base branch to dev.

[lahirumaramba]

I've changed base branch to dev.

Thank you!!

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[lahirumaramba]

@googlebot I fixed it.