MNT: make pre-release notes script check if EDITOR is set

[nstelter-slac]

Description

Motivation and Context

closes #326

How Has This Been Tested?

Tested manually

Where Has This Been Documented?

don't think it's necessary for this

Pre-merge checklist

• Code works interactively
• Code contains descriptive docstrings, including context and API
• New/changed functions and methods are covered in the test suite where possible
• Test suite passes locally
• Test suite passes on GitHub Actions
• Ran docs/pre-release-notes.sh and created a pre-release documentation page
• Pre-release docs include context, functional descriptions, and contributors as appropriate

[nstelter-slac]

should prob also update the other pre-release scripts b4 closing issue: https://github.com/search?q=org%3Apcdshub+if+%24%7BEDITOR%7D&type=code

[nstelter-slac]

actually lets just only also update cookie-cutter for now: pcdshub/cookiecutter-pcds-python#55

[ZLLentz]

Sensible and helpful default

[ZLLentz]

Merging once the CI finishes churning

[tangkong]

LGTM. Cookiecutter changes won't immediately propagate to all our packages, but that's ok and doesn't stop this from being mergable