Multiple-cursors module - evil-mc-toggle-cursor-on-click

### Describe your request

I'd like the inclusion of the function `evil-mc-toggle-cursor-on-click` from `evil-mc`, so that one can create new cursors using some mouse event. I suggest mapping it to `C-S-`. This function is mentioned in the [issue 56](https://github.com/gabesoft/evil-mc/issues/56) of `evil-mc`.

### Briefly explain its use-case

Sometimes there is not really a pattern for where you want to create another cursor and if you already have the mouse in hand it is convenient to create them using the mouse. For example, in a long math formula in a TeX document, sometimes one wants to add a term but it appears in different positions and there is no real pattern to use visual selection and `M-d`.