feat: Add a Github Action that automatically closes stale PRs.

[maniarathi]

Reason for Change

As we move to CI/CD, some automation can help ensure that we're working towards trunk-based development and ensuring that non-draft PRs don't stay open too long without some movement. Ideally, this Github Action helps us with a few things:

1. PRs remain small so that they can be reviewed quickly and merged.
2. If a PR has be alive for more than 2 weeks, updates are required so that there is visibility as to why the PR is blocked.
3. If the PR has to be alive for more than 2 weeks and is blocked, it reverts to being a draft PR or closed.

Ticket Number

No ticket.

Changes

Additions

Add a Github Action that runs daily. Each day all active (non-draft) PRs older than 2 weeks are marked with a stale tag and a warning comment is made to update the PR. In another 3 days (3 days was chosen to accommodate long weekends + 1 day), the PR will be automatically closed.

Deletions

None.

Modifications

None.

Testing steps

Not tested.

Notes for Reviewer

None.

[codecov]

Codecov Report

Merging #647 (e0c7efb) into main (2a8496f) will not change coverage.
The diff coverage is n/a.

❗ Current head e0c7efb differs from pull request most recent head 8df9f19. Consider uploading reports for the commit 8df9f19 to get more accurate results

@@           Coverage Diff           @@
##             main     #647   +/-   ##
=======================================
  Coverage   77.67%   77.67%           
=======================================
  Files          88       88           
  Lines        6754     6754           
=======================================
  Hits         5246     5246           
  Misses       1508     1508           

Flag	Coverage Δ
frontend	77.67% <ø> (ø)
javascript	77.67% <ø> (ø)
smokeTest	?
unitTest	77.67% <ø> (ø)

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