Release 0.7.0

Prepare for release 0.7.0 

FEATURES
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- [Canonical Assertion](https://github.com/twada/espower/pull/8)
- [String diff (or expected/actual) reporting on BinaryExpression](https://github.com/twada/power-assert-formatter/pull/4)
- [Depth-limited custom stringify function](https://github.com/twada/power-assert-formatter/pull/6)

TODO
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- [x] Update dependencies
- [x] Update documents
- [x] Maint tests
- [x] Maint sandbox