Adds output flag

[ajmeese7]

Allows users to redirect output to a file instead of stdout if they prefer. Useful when writing automation scripts.

[brianokinyi]

I get this error when I run without --output flag:

Traceback (most recent call last):
File "/usr/bin/crtsh", line 48, in
file = open(args.output, "w")
^^^^^^^^^^^^^^^^^^^^^^
TypeError: expected str, bytes or os.PathLike object, not NoneType

[ajmeese7]

Good catch @brianokinyi, that should fix it. Didn't test extensively for this PR, obviously.