Add support for {} imports

[corollari]

Title is self-explanatory, this just adds support for imports of the type import {Contract} from "something.sol";

[corollari]

Related to #1

[PaulRBerg]

Hey Albert, thanks for your PR.

I ran your modified regex expression on regexr.com and unfortunately it didn't match the {} imports:

[corollari]

When the string \\ gets evaluated by the rust compiler it becomes \, so what is getting actually passed to the regex matcher is import (?:\{[^{}]*\} from )?['\"](.*?.sol)['\"]; (actually \" also becomes ", but this is irrelevant)

[corollari]

@PaulRBerg thoughts?

[PaulRBerg]

Hey Albert, your follow-up comment fell through the cracks for me. I will look at this during the weekend and very likely include your proposed change as part of [email protected]

[PaulRBerg]

Thanks for your contribution, @corollari! I just shipped it via v1.1.0.