update template to explain about keeping all sections
Add a note to the process at the top of the template explaining that
all required sections must be kept in the published doc.
@@ -62,6 +62,9 @@ To get started with this template:
of the platform. Aim for single topic PRs to keep discussions focused. If you
disagree with what is already in a document, open a new PR with suggested
changes.
+1. **Keep all required headers.** If a section does not apply to an
+ enhancement, explain why but do not remove the section. This part
+ of the process is enforced by the linter CI job.
The `Metadata` section above is intended to support the creation of tooling
around the enhancement process.
