Add data-task and tag classes

[deathau]

For my own benefit, I added in the data-task element on the timeline DIVs, as it has been for checkboxes in preview mode from Obsidian 0.12.0. This allows me to style elements on the timeline according to checkbox type.
For example, I can use - [-] to indicate something that has been cancelled, and apply a CSS class for [data-task='-'] to grey out the box on the timeline to indicate that cancellation.

Furthermore, I've added any tags as classes on the block, so I can highlight #meeting tasks (or any other arbitrary tag I like).

[deathau]

Visual example:

[lynchjames]

I resolved some conflicts from other upstream PRs but your change to use completion as a string instead of a bool is now causing some newly introduced tests to fail to compile.

Could you commit a fix?

[ivan-lednev]

Closing this as stale.