Add GitHub Action to Auto-Label PRs with ECWoC26

[neeru24]

To streamline PR management for ECWoC26, we should automatically add the ECWoC26 label whenever a new Pull Request is opened. This helps maintain consistency, improves visibility, and reduces manual effort for maintainers.

Currently, labels need to be added manually, which is error-prone—especially for PRs coming from forks.

@abhishek-nexgen-dev

[github-actions]

Thank you for raising this issue!

We'll review it as soon as possible. We truly appreciate your contributions! ✨

Meanwhile make sure you've visited the README.md, CONTRIBUTING.md, and CODE_OF_CONDUCT.md before creating a PR for this. Also, please do NOT create a PR until this issue has been assigned to you. 😊