Ability to add annotations to chart

[yanofsky]

[yanofsky]

Features

• [x] Add new annotation
• [x] Delete annotation
• [x] Edit annotation text inline
• [x] Edit annotation text in editor
• [x] Move arrow inline
• [x] Make arrow optional
• [x] Have character count/limit on text
• [x] Edit direction of arrow in editor
• [ ] Snap to corner for arrow start point
• [ ] Snap to end of text for arrow start point
• [x] Have alternate display for mobile
• [ ] Change chart rendering to be able to handle html elements
• [ ] Change SVG output to be able to handle html elements

Bugs

• [x] Blurb layer blocks label layer from mouse events
• [ ] Arrow direction toggle doesn't flip when arrow direction is directly edited
• [ ] Use value based positioning
• [ ] Mobile display is ugly