Fix button-highlighting and visual feedback

data/style.css: Highlight "wide"-outline

The "wide"-outline was not highlighted on the default and high contrast styles, while it was highlighted on the "Adwaita:dark"-style. "Adwaita:dark" is the default on Phosh, so adjust to that, for consistent button-highlighting.

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Adwaita:dark: Add visual feedback when pressing highlighted buttons

Before this change, buttons with the outlines "altline", "wide" and "special" were not showing visual feedback when those were pressed.

After this change, the visual feedback is similar to the default style.

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Fixes #401 (closed)