Drop Python 3.7 and minor improvements

What's Changed

• Validate order of area and columns by @chezou in #331
• Apply grammarly for documents by @chezou in #334
• fix: do not break pandas_options by @chezou in #339
• Allow Iterable as much as possible by @chezou in #340
• Drop Python 3.7 by @chezou in #341
• Fix package build on CI by @chezou in #342

Full Changelog: v2.6.0...v2.7.0rc