[Bug] view-rule passes path as string

[ghost]

Describe the bug
When using the view-rule command the program crashes with a stack trace:

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█  █ █▄▄  █  █▄▄ █    █   █  █ █ █▀▄ █      █▄▄▀ █  █ █   █▄▄ █▄▄
█▄▄▀ █▄▄  █  █▄▄ █▄▄  █  ▄█▄ █▄█ █ ▀▄█      █ ▀▄ █▄▄█ █▄▄ █▄▄ ▄▄█

rules/network/command_and_control_cobalt_strike_beacon.toml
Error loading rule in rules/network/command_and_control_cobalt_strike_beacon.toml
Traceback (most recent call last):
  File "/usr/lib/python3.8/runpy.py", line 194, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.8/runpy.py", line 87, in _run_code
    exec(code, run_globals)
  File "/home/code/git/detection-rules/detection_rules/__main__.py", line 34, in <module>
    main()
  File "/home/code/git/detection-rules/detection_rules/__main__.py", line 31, in main
    root(prog_name="detection_rules")
  File "/home/code/git/detection-rules/env/detection-rules-build/lib/python3.8/site-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/home/code/git/detection-rules/env/detection-rules-build/lib/python3.8/site-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/home/code/git/detection-rules/env/detection-rules-build/lib/python3.8/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/code/git/detection-rules/env/detection-rules-build/lib/python3.8/site-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/code/git/detection-rules/env/detection-rules-build/lib/python3.8/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/home/code/git/detection-rules/env/detection-rules-build/lib/python3.8/site-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/home/code/git/detection-rules/detection_rules/main.py", line 164, in view_rule
    rule = RuleCollection().load_file(rule_file)
  File "/home/code/git/detection-rules/detection_rules/rule_loader.py", line 209, in load_file
    path = path.resolve()
AttributeError: 'str' object has no attribute 'resolve'

To Reproduce
$ env/detection-rules-build/bin/python -m detection_rules view-rule rules/network/command_and_control_cobalt_strike_beacon.toml

Expected behavior
Show the rule content

Desktop (please complete the following information):

• OS: Ubuntu
• Version: 20.04

Additional context

The problem is in main.py. We could replace:

rule = RuleCollection().load_file(rule_file)

with:

rule = RuleCollection().load_file(Path(rule_file))