0.9 planning

[henryiii]

I'd like to work on the following then get a release out:

• #697
• https://github.com/orgs/scikit-build/discussions/1075 - this would be by adding SKBUILD_METADATA_DIR
• #709 Make multiline description an error (with minimum-version check)
• #703
• #708
• Make the other pyproject backend lib required (empty pyproject extra) #711
• Use metadata 2.2 (postponed so we can make sure interaction with dynamic-metadata is correct.)

I removed #663 - I think this might not be incorrect, waiting for user update.