REL/DOC: release notes for v3.1.0, make release script run on windows

[ZLLentz]

Description

• Compile release notes for v3.1.0
• Adjust the release notes script to run on my local windows machine by forcing a sane encoding

Motivation and Context

• Let's make a quick tag for the updates merged today so they'll be available on pypi/conda-forge soon
• I'm currently working locally for once (planned power outage), and windows does not have a sane encoding default

How Has This Been Tested?

• Interactively only

Where Has This Been Documented?

• This is docs

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
• Code has been checked for threading issues (no blocking tasks in GUI thread)
• 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

[tangkong]

LGTM. 🏷️