Feature request re font sizes

Would be great if we could add classes to ignore for increase / decrease fonts or somehow set a max font size for some elements. There's occasions where increasing the font will break menu or uglify the site too much.

The issue names no files, tests, or entry points. Start by reviewing the plugin's font-size controls and how they affect menus and other elements; done should provide a defined way to prevent selected elements from being enlarged or reduced without breaking the site.

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