Added info about CI-related labels to the PR template (#17446)

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,6 +1,19 @@
 <!-- Add brave-browser issue below that this PR will resolve -->
 Resolves 
 
+<!-- CI-related labels that can be applied to this PR:
+* CI/run-audit-deps (1) - check for known npm/cargo vulnerabilities (audit_deps)
+* CI/run-draft - run CI builds on a draft PR (otherwise only on non-draft PRs)
+* CI/run-network-audit (1) - run network-audit
+* CI/run-upstream-tests - run Chromium unit and browser tests on Linux and Windows (otherwise only on Linux)
+* CI/skip - do not run CI builds (except noplatform)
+* CI/skip-linux, CI/skip-android, CI/skip-macos, CI/skip-ios, CI/skip-windows, CI/skip-windows-x86 - skip CI builds for specific platforms
+* CI/skip-upstream-tests - do not run Chromium unit, or browser tests (otherwise only on Linux)
+* CI/storybook-url (1) - deploy storybook and provide a unique URL for each build
+
+(1) applied automatically when some files are changed (see: https://github.com/brave/brave-core/blob/master/.github/labeler.yml)
+-->
+
 ## Submitter Checklist:
 
 - [ ] I confirm that no security/privacy review [is needed](https://github.com/brave/brave-browser/wiki/Security-reviews), or that I have [requested](https://github.com/brave/security/issues/new/choose) one