Merge pull request #2108 from w3c/tc-pr-template

Add PR template

.github/pull_request_template.md

@@ -0,0 +1,19 @@
+Closes #???
+
+<!-- Remove the following for non-normative changes -->
+
+The following tasks have been completed:
+
+- [ ] Modified Web platform tests ([link](https://github.com/web-platform-tests/wpt/))
+
+Implementation commitment:
+
+- [ ] WebKit ([link to issue](https://bugs.webkit.org/))
+- [ ] Chromium ([link to issue](https://issues.chromium.org/issues/new?component=1456855&template=0))
+- [ ] Gecko ([link to issue](https://bugzilla.mozilla.org/home))
+
+Documentation and checks
+
+- [ ] Affects privacy
+- [ ] Affects security
+- [ ] Updated explainer ([link](https://github.com/w3c/webauthn/wiki)