Update for Python 3.11

[jmcvey3]

Code fixes to remove dependency on older netCDF4 package. Also fixes bug where prior variable encoding was dropped.

[jmcvey3]

Resolves Issue #115

[coveralls]

Pull Request Test Coverage Report for Build 7145562198

• 24 of 25 (96.0%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.01%) to 89.303%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
dolfyn/io/api.py	19	20	95.0%
<!--	Total:	24	25	96.0%	-->

Files with Coverage Reduction	New Missed Lines	%
dolfyn/io/api.py	1	92.81%
<!--	Total:	1		-->

Totals
Change from base Build 6788370525:	0.01%
Covered Lines:	5393
Relevant Lines:	6039

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💛 - Coveralls

[jmcvey3]

Also added updates and fixes for ReadtheDocs