docs: keep the Commit Type checklist in the external PR template

Review feedback on triton-inference-server/server#8890: external
contributors keep the visual commit-type checklist for now; internal
contributors rely on the enforced conventional-pr workflow and
commit-msg hook.

TRI-1100

Author: mc-nv

PULL_REQUEST_TEMPLATE/pull_request_template_external_contrib.md

@@ -16,6 +16,20 @@ Agreement](https://github.com/NVIDIA/triton-inference-server/blob/master/Triton-
 - [ ] All template sections are filled out.
 - [ ] Optional: Additional screenshots for behavior/output changes with before/after.
 
+#### Commit Type:
+Check the [conventional commit type](https://github.com/angular/angular/blob/22b96b9/CONTRIBUTING.md#type)
+box here and add the label to the github PR.
+- [ ] build
+- [ ] ci
+- [ ] docs
+- [ ] feat
+- [ ] fix
+- [ ] perf
+- [ ] refactor
+- [ ] revert
+- [ ] style
+- [ ] test
+
 #### Related PRs:
 <!-- Related PRs from other Repositories -->