Add automatic font height

[Nicolas-Ferre]

Problem
Currently the font height should be manually specified, which is not always convenient:

• If text size is too big, the text will be blurred.
• If text size is too small, the text quality might not be optimal.

Feature
Add automatic font height.

Additional context

• Investigate SDF fonts (e.g. https://github.com/gabdube/easy-signed-distance-field)