* don't set a value in annotationStorage by default:
- having an undefined when the annotation is rendered for saving/printing means nothing has changed so use normal appearance
- aims to fix https://bugzilla.mozilla.org/show_bug.cgi?id=1681687
* change the way to compute font size when this one is null in DA:
- make fontSize proportional to line height
- in multiline case, take into account the number of lines for text entered to adapt the font size