Prepare for dartdoc 0.32.0 (dart-lang#2159)

Prepare for dartdoc-0.30.1 (dart-lang#2127)

* Prepare for dartdoc-0.30.1

* Update changelog for latest changes

* Update changelog

* Reformat changelog

Prepare for dartdoc 0.30.0+1 (dart-lang#2119)

* Fix basehref for search box on non-root cases

* Use src element and correct relative path for directory return value

* Prepare for 0.30.0+1

Prepare for dartdoc-0.39.0 (dart-lang#2116)

Prepare for dartdoc 0.29.3. (dart-lang#2095)

Prepare for dartdoc 0.29.2 (dart-lang#2083)

* Prepare for dartdoc 0.29.2

* Add last couple PRs to Changelog

Prepare for version 0.29.1 (dart-lang#2066)

Prepare for dartdoc 0.29.0 (dart-lang#2054)

* Prepare for dartdoc 0.29.0

* Reword changelog

Update CHANGELOG and version for 0.28.8 (dart-lang#2041)

Prepare for dartdoc 0.28.7 (dart-lang#2035)

* Prepare for dartdoc 0.28.7

* Update CHANGELOG to reflect newest bugfix