Improve the readability of the Rubin user guide theme:
Increase base font size from 15px to 18px (which allows us to reduce line height from 1.65 to 1.5)
Reduce contrast of table border lines in dark mode
Fix a CSS bug that caused the GitHub icon in the top right to be smaller (now it's set to var(--pst-font-size-icon), which should be future proof and the theme's intent.
Improve the readability of the Rubin user guide theme:
var(--pst-font-size-icon), which should be future proof and the theme's intent.Finally release as version 0.7.0.