Support providing version of crx3 tool

[przemoc]

I realized there is no easy way to confirm version of crx3 tool. Please consider fixing it.

Typically it is done via options:
-V, --version
(upper-case V, because lower-case v is typically used for increasing verboseness)

But you could also do it via command:
version

[mmadfox]

Okay. I will add it soon, and it is a very useful command