bug: CLI fails if missing plugins

[pesap]

cli_functions.py is raising import error if plugin not found. We should just skip the plugin.

[llavin13]

I guess just note on my end I seem to hit an error similar to this if I try to r2x init. I assume this is expected behavior for now?

Traceback (most recent call last):
  File "/home/llavin/.conda-envs/r2x/bin/r2x", line 8, in <module>
    sys.exit(cli())
             ^^^^^
  File "/kfs2/projects/ntps/llavin/R2X/src/r2x/cli.py", line 17, in cli
    parser = base_cli()
             ^^^^^^^^^^
  File "/kfs2/projects/ntps/llavin/R2X/src/r2x/cli_functions.py", line 172, in base_cli
    _ = get_additional_arguments(run_command)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/kfs2/projects/ntps/llavin/R2X/src/r2x/cli_functions.py", line 66, in get_additional_arguments
    package_script = importlib.import_module(f"{package}")
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/llavin/.conda-envs/r2x/lib/python3.11/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<frozen importlib._bootstrap>", line 1204, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1176, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1140, in _find_and_load_unlocked
ModuleNotFoundError: No module named 'r2x.plugins.cambium'