Update semgrep.yml

[hrushikeshdeshpande]

What kind of change does this PR introduce?

Updating Semgrep.yml file - Semgrep is a tool that will be used to scan Cloudflare's public repos for Supply chain, code and secrets. This work is part of Application & Product Security team's initiative to onboard Semgrep onto all of Cloudflare's public repos.

In case of any questions, please reach out to "Hrushikesh Deshpande" on cf internal chat.

Did you add tests for your changes?

This has been tested on a test repo.

Summary

Semgrep will run a scan on every PR and on main/master branch everyday. Does this PR introduce a breaking change?

No

Other information