Support testing decorations

[pokey]

We'd basically do all decorations through a mockable interface and then dump them along with the rest of the yaml. For actions that decorate twice, we could track both, and compare document contents at time of decoration to initial and final state, and then store them as pre- or post-decoration based on that

see https://github.com/cursorless-dev/cursorless/blob/main/src/core/editStyles.ts

[AndreasArvidsson]

First draft

thatMark:
    - anchor: {line: 2, character: 4}
      active: {line: 2, character: 4}
    - anchor: {line: 4, character: 0}
      active: {line: 4, character: 0}
decorations:
    - name: pendingDeleteBackground
      type: token
      start: {line: 2, character: 4}
      end: {line: 2, character: 10}
    - name: pendingDeleteBackground
      type: line
      start: {line: 4, character: 4}
      end: {line: 4, character: 18}

[pokey]

cool! I'm assuming that decorations will be top-level indent?

[AndreasArvidsson]

Correct. It is, something weird happened when I pasted it