Feature request: unary operators

[t1u1]

It would be nice if unary operators are detected.

For example, a - -b can be parsed and rendered as:

<mi>a</mi><mo>−</mo><mrow><mi>-b</mi></mrow>

instead of

<mi>a</mi><mo>−</mo><mrow><mo>−</mo><mi>b</mi></mrow>

Edit: If the above is difficult, then it could be detected in unfenced groups. For example: a - {: -b :}