4.2.0 contains versionless dep on importlib_resources

[eddie-scio]

Could we add version boundaries here like we do for other libraries? Older versions (e.g. 1.0.2) of importlib_resources (if pinned) will throw errors like below

  File "/env/lib/python3.7/site-packages/jsonschema/__init__.py", line 29, in <module> 
    from jsonschema.validators import ( 
  File "/env/lib/python3.7/site-packages/jsonschema/validators.py", line 349, in <module> 
    meta_schema=_utils.load_schema("draft3"), 
  File "/env/lib/python3.7/site-packages/jsonschema/_utils.py", line 60, in load_schema 
    path = resources.files(__package__).joinpath(f"schemas/{name}.json") 
AttributeError: module 'importlib_resources' has no attribute 'files' 

[Julian]

Sure, happy to see a PR pinning importlib-resources from below.