Option --files does not work because a pattern is always sent to rg

[vgadoury]

Describe the bug
The option --riles (rg.files()) does not work because a pattern is always sent to ripgrep. From the ripgrep usage, the --files option must be used without a pattern, and all additional arguments are considered as paths:

rg [OPTIONS] --files [PATH ...]

To Reproduce

>>> from ripgrepy import Ripgrepy
>>> Ripgrepy("", "./ripgrepy/").files().run()
: The system cannot find the path specified. (os error 3)

>>> res = Ripgrepy("", "./ripgrepy/").files().run()
>>> res.command
['rg', '--files', '', './ripgrepy/']
>>> # Running the command `rg --files "" ./ripgrepy/` gives the same error:
>>> import subprocess
>>> subprocess.run(['rg', '--files', '', './ripgrepy/'])
: The system cannot find the path specified. (os error 3)
./ripgrepy/__pycache__\__init__.cpython-38.pyc
./ripgrepy/__init__.py
CompletedProcess(args=['rg', '--files', '', './ripgrepy/'], returncode=2)

Expected behavior

>>> # We should run `rg --files ./ripgrepy/` instead:
>>> subprocess.run(['rg', '--files', './ripgrepy/'])
./ripgrepy/__pycache__\__init__.cpython-38.pyc
./ripgrepy/__init__.py
CompletedProcess(args=['rg', '--files', './ripgrepy/'], returncode=0)

The expected output would be:

>>> Ripgrepy("", "./ripgrepy/").files().run()
./ripgrepy/__pycache__\__init__.cpython-38.pyc
./ripgrepy/__init__.py

>>> Ripgrepy("", "./ripgrepy/").files().run().as_string
'./ripgrepy/__pycache__\\__init__.cpython-38.pyc\n./ripgrepy/__init__.py\n'

Desktop:

• OS: tested on Windows 10, but rg --files returns the same "os error 2" on Ubuntu when providing a non-path argument.
• Python Version 3.8.5

Additional context
I'll send a PR shortly. I guessed it was better to explain the issue before posting a PR?