introduce a Line class (dart-lang/markdown#494)

* introduce a Line class

* Update CHANGELOG

* maintain backwards compatibility

* Update CHANGELOG

* Improve CHANGELOG.md

* Improve CHANGELOG.md

* Add more comment for tabRemaining

* Remove toMap from Line

* set `isBlankLine` of `Line` as final

* remove extension name LineX
22 files changed
tree: b8ea882cb9dbe6b54eb8c6c495c7a277145100cf
  1. pkgs/