Add icons for flycheck and smartparens

[cprussin]

These are two modes I use heavily and would love to have icons for them. Would you accept a PR to add them?

Flycheck has a website with a favicon that I can use, for smartparens I had something like this in mind: https://www.computerhope.com/jargon/p/parenthesis.gif

[mattfidler]

Of course. Submit a pull request