Feature Request: Single line for '--' for BEM style css

[ryansh100]

Noticed that BEM style css modifiers could be a lot smoother if there was a solid straight line for the '--' character combination.

[SSNikolaevich]

I don't like how solid line looks in this cases: i--, --i. But '--' needs to be a ligature with less space between minus signs in order to match '++' ligature width.