Node descriptions

[taramk]

• description uses color-text-secondary
• font: [either 12px or 13px], line height 150%
• command palette > Add Description produces an empty description field with placeholder text “Add Description”. Similarly, command palette should have a "Remove Description" option for nodes that have a description.
• show description when node is header as well, styled the same but with a slight top margin on the description
• don’t allow adding descriptions to non-editable nodes (smart node children, for example)

figma: https://www.figma.com/file/bGzEZo0NYHhWGJO95kwF3p/Treehouse-App?type=design&node-id=504%3A8057&mode=design&t=d6LlVs7KaDchiyNU-1

[taramk]

@progrium i think either 12px or 13px would work, do you have a preference? i initially tried 14px but it's too big, the description should be less obtrusive.

comparisons here: https://www.figma.com/file/bGzEZo0NYHhWGJO95kwF3p/Treehouse-App?type=design&node-id=505%3A8185&mode=design&t=d6LlVs7KaDchiyNU-1

also, i think descriptions will look fine on most node types. mocked it up on documents and headers as seen here: https://www.figma.com/file/bGzEZo0NYHhWGJO95kwF3p/Treehouse-App?type=design&node-id=504%3A8057&mode=design&t=d6LlVs7KaDchiyNU-1