Bump to v2.0.0a10

[shinaoka]

Summary

Bump version to 2.0.0a10.

This PR also includes recent documentation improvements:

• Added release process documentation to README
• Added pylibsparseir dependency update procedure to README

Changes

• pyproject.toml: version 2.0.0a9 → 2.0.0a10
• .conda/meta.yaml: automatically reads version from pyproject.toml

After Merge

After merging this PR to mainline:

1. Create and push tag:

   git checkout mainline
   git pull origin mainline
   git tag v2.0.0a10
   git push origin v2.0.0a10

2. Automated builds will trigger:

   • PyPI: wheel.yml workflow
   • conda: conda.yml workflow (SpM-lab channel)