0.4.20

Some feature work (mostly by other contributors) while I while away at section metadata. May also fix a few bugs!

• Fix #448: You can now use the "Task Completion Tracking" option to automatically add completion metadata to tasks
  which are checked/unchecked through Dataview. Thanks to @sheeley.
• Add a search bar to documentation. Thanks to @tzhou.
• Add new date expressions for the start of the week (date(sow)), and the end of the week (date(eow)). Thanks
  @Jeamee and @v_mujunma.

Small minor bugfix / security releases may follow in the near future; otherwise, the next major release will include
section and object metadata.