Add a release/dev.txt file and include it from release/index.rst in
development versions. Add a "Changes Since Release" section with a
toctree that globs adjacent "dev/*" documents. Add a sample topic
document explaining how topic-specific release note documents work.
This approach will allow developers to write release notes for their
changes as they are made. The release manager may then consolidate and
organize the notes for a specific release version.
Add a release/index.rst document titled "CMake Release Notes" to hold
the toctree for release notes. Add a "Release Notes" section to the
top-level html document index to link to the new document.
