Add gitleaks repo scan and submit github security scanning alert

[haani-niyaz]

Change

Contains the github workflow to:

1. Run gitleaks secret scanning on repo
2. On detection, submit Github security alert

Closes #3 .

Considerations

GH actions for gitleaks requires licensing for organization repositories as per https://github.com/marketplace/actions/gitleaks#do-i-need-a-license-key therefore this has been somewhat hand crafted.

Sample results

Can be viewed here https://github.com/haani-niyaz/gitleaks-gh-action-sample/actions/runs/2532666777

Security alert can be viewed from Security (tab) -> Code scanning alerts (menu option).

[haani-niyaz]

@shukra-in-spirit, pre-commit white-space error fixed.