Clarify paths in templates/software process, fix formatting

[rly]

From @ajtritt 's suggestions, this PRs adds paths to the filenames in the PR templates and fixes formatting. Also fixes a minor sphinx warning.

Checklist

• If the current schema version on "master" is a public release:

  • [ ] Update the version string in conf.py and namespace.yaml to the next version with the suffix "-alpha"
  • [ ] Add a new section in the release notes for the new version with the date "Upcoming"

• [x] Add release notes for the PR - release notes for the software process have already been added

See https://hdmf-common-schema.readthedocs.io/en/latest/software_process.html for more details.