Add md5 hash property to GSPath

[fafnirZ]

Adding md5 property into GSPath
Updating supported methods and properties in repository root README
Updating LocalGSPath to mimic LocalAzureBlobPath, in that there exists md5 property
Updating mock_gs.MockBlob to include md5_hash property

Closes #482

---

Contributor checklist:

• I have read and understood CONTRIBUTING.md
• Confirmed an issue exists for the PR, and the text Closes #issue appears in the PR summary (e.g., Closes #123).
• Confirmed PR is rebased onto the latest base
• Confirmed failure before change and success after change
• Any generic new functionality is replicated across cloud providers if necessary
• Tested manually against live server backend for at least one provider
• Added tests for any new functionality
• Linting passes locally
• Tests pass locally
• Updated HISTORY.md with the issue that is addressed and the PR you are submitting. If the top section is not `## UNRELEASED``, then you need to add a new section to the top of the document for your change.

[pjbull]

Thanks @fafnirZ! Could you CI failures and add a new test?

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 93.1%. Comparing base (7f1a5dc) to head (2ea689a).
Report is 1 commits behind head on 483-local-tests.

Files with missing lines	Patch %	Lines
cloudpathlib/gs/gspath.py	85.7%	1 Missing ⚠️
cloudpathlib/local/implementations/gs.py	66.6%	1 Missing ⚠️

Additional details and impacted files

@@                Coverage Diff                @@
##           483-local-tests    #483     +/-   ##
=================================================
- Coverage             94.4%   93.1%   -1.4%     
=================================================
  Files                   23      23             
  Lines                 1776    1785      +9     
=================================================
- Hits                  1678    1663     -15     
- Misses                  98     122     +24     

Files with missing lines	Coverage Δ
cloudpathlib/gs/gsclient.py	90.0% <ø> (-1.5%)	⬇️
cloudpathlib/gs/gspath.py	92.4% <85.7%> (-1.2%)	⬇️
cloudpathlib/local/implementations/gs.py	97.1% <66.6%> (-2.9%)	⬇️

... and 2 files with indirect coverage changes

[fafnirZ]

Hey @pjbull, I'm kinda confused as to why my changes has caused so many seemingly unrelated tests to fail on the live server, any chance you could point me in the right direction?

[pjbull]

Sorry, as noted here, those are expected since PRs from forks can't access the credentials:
https://cloudpathlib.drivendata.org/stable/contributing/#pr-cicd-test-run

[fafnirZ]

Thanks for the response!
Ohhh I missed that section, my bad haha. was getting worried for a second and was thinking I made a big mistake😅.
All goods then! everything seems to look fine then I think?

Lmk if there are any issues with this PR! :)