Ready for 0.7.0 PyPI/GitHub release

[bobleesj]

Release checklist for GitHub contributors

• [x] All PRs/issues attached to the release are merged.
• [x] All the badges on the README are passing. current CI status fails because we tested against 3.10 before
• [x] License information is verified as correct. If you are unsure, please comment below.
• [x] Locally rendered documentation contains all appropriate pages, including API references (check no modules are missing), tutorials, and other human written text is up-to-date with any changes in the code.
• [x] Installation instructions in the README, documentation and on the website (e.g., diffpy.org) are updated and tested
• [x] Successfully run any tutorial examples or do functional testing in some other way.
• [x] Grammar and writing quality have been checked (no typos).

Ready for pre-release on PyPI. Tests conducted here: https://github.com/diffpy/diffpy.srmise/pull/143

• Support Python 3.13, hence bumped from 0.6.1 to 0.7.0

[bobleesj]

@sbillinge ready for pre-release