Css Important option

[flyingL123]

I am currently integrating Tailwind.css into an existing website. Tailwind allows you to specify an important option in its configuration which makes all of their style declarations include the !important flag. See documentation here.

This is very useful when transitioning an existing project to Tailwind so that the new styles will override existing style sheets. I was also attempting to use this library in that same project, but was finding that the styles being applied weren't working because sometimes they were getting overridden by Tailwind styles.

This PR allows for a cssImportant option which simply adds the !important flag to the plugin's generated css. After adding this option, the plugin worked great even with Tailwind's important styles in place.