Add support for css modules

[arjanvillon]

This is a great package! Great work guys. I just want to suggest a new feature to support css modules when adding a className or columnClassName.

[mienaikoe]

I'm using css modules with react-masonry-css, albeit in a basic way. What is missing that prevents you from using css modules?

[fondberg]

Can you provide an example?

[C-Garza]

Could you not do something like this?:

      <Masonry 
        breakpointCols={3}
        className={`${styles.grid}`}
        columnClassName={styles.grid__column}
      >
        {/* array of JSX items */}
      </Masonry>