add secret scanning workflow (#11053)

**What this PR does / why we need it**:
Short PR to add GitHub Action workflow to run Trufflehog on each PR.
Will only fail/alert on verified secrets. This can be tweaked and
configured later if need be.

**Which issue(s) this PR fixes**:
Fixes #<issue number>

**Special notes for your reviewer**:

**Checklist**
- [ ] Reviewed the
[`CONTRIBUTING.md`](https://github.com/grafana/loki/blob/main/CONTRIBUTING.md)
guide (**required**)
- [ ] Documentation added
- [ ] Tests updated
- [ ] `CHANGELOG.md` updated
- [ ] If the change is worth mentioning in the release notes, add
`add-to-release-notes` label
- [ ] Changes that require user attention or interaction to upgrade are
documented in `docs/sources/setup/upgrade/_index.md`
- [ ] For Helm chart changes bump the Helm chart version in
`production/helm/loki/Chart.yaml` and update
`production/helm/loki/CHANGELOG.md` and
`production/helm/loki/README.md`. [Example
PR](d10549e)
- [ ] If the change is deprecating or removing a configuration option,
update the `deprecated-config.yaml` and `deleted-config.yaml` files
respectively in the `tools/deprecated-config-checker` directory. <!--
TODO(salvacorts): Add example PR -->

Co-authored-by: Michel Hollands <[email protected]>

.github/workflows/secret-scanning.yml

@@ -0,0 +1,17 @@
+name: TruffleHog Secrets Scan
+on: [pull_request]
+jobs:
+  TruffleHog:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+      - name: TruffleHog OSS
+        uses: trufflesecurity/trufflehog@main
+        with:
+          path: ./
+          base: ${{ github.event.repository.default_branch }}
+          head: HEAD
+          extra_args: --debug --only-verified