Add warning if writing file without .nwb.zarr file extension

[stephprince]

Motivation

Fix #230. Add a warning if writing a Zarr NWBFile that does not end in .nwb.zarr.

How to test the behavior?

from datetime import datetime
from dateutil.tz import tzutc
from pynwb import NWBFile
from hdmf_zarr import NWBZarrIO

nwbfile = NWBFile(session_description='a test NWB File',
                                identifier='TEST123',
                                session_start_time=datetime(1970, 1, 1, 12, tzinfo=tzutc()))
with NWBZarrIO("path.h5", 'w') as io:
    io.write(nwbfile)

Warns with:

UserWarning: The file path provided: path.h5 does not end in '.nwb.zarr'. It is recommended that NWB files using the Zarr backend use the '.nwb.zarr' extension
  warnings.warn(f"The file path provided: {path} does not end in '.nwb.zarr'. "

Checklist

• Did you update CHANGELOG.md with your changes?
• Does the PR clearly describe the problem and the solution?
• Have you reviewed our Contributing Guide?
• Does the PR use "Fix #XXX" notation to tell GitHub to close the relevant issue numbered XXX when the PR is merged?

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.07%. Comparing base (b5b3ce6) to head (4625a4f).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #265      +/-   ##
==========================================
+ Coverage   86.87%   87.07%   +0.19%     
==========================================
  Files           5        5              
  Lines        1196     1199       +3     
  Branches      227      228       +1     
==========================================
+ Hits         1039     1044       +5     
+ Misses         98       97       -1     
+ Partials       59       58       -1     

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