Documentation: Explain ratio relationship between height, width, and font size

To support scaling rendering, `width`, `height`, and `font size` do not reflect absolute units but rather proportions. In printing to custom media such as die cut labels it would reduce the amount of trial and error to have the proportional relationships between those values documented. Specifically a couple sentences in the `options` documentation would suffice:
1. Using the defaults for `width: 2` and `height: 100` as an example state what the aspect ratio of the rectangle of the smallest *"unguarded"* line would be.
2. Using the defaults for `width: 2` and `font size: 20` as an example state what the ratio between the smallest line and the font scale would be. Analogous to a *"psuedo-point"* relative to the smallest line width.

Locate the options documentation and review how the default width, height, and font size are described. Add the two requested proportional relationships using the stated defaults, then verify that the wording clearly explains the smallest unguarded line and the font scale.

Written by the indexing model from the issue text.