[WIP] Adding some docstrings

[hehouts]

adding docs strings to cli/, minhash.py and sig.py
Chips away at #1563

[codecov]

Codecov Report

Merging #1583 (718aa04) into latest (a782b1d) will decrease coverage by 0.92%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           latest    #1583      +/-   ##
==========================================
- Coverage   90.20%   89.28%   -0.93%     
==========================================
  Files         126       75      -51     
  Lines       21194     6626   -14568     
  Branches     1595     1171     -424     
==========================================
- Hits        19118     5916   -13202     
+ Misses       1844      505    -1339     
+ Partials      232      205      -27     

Flag	Coverage Δ
python	89.28% <100.00%> (-5.92%)	⬇️
rust	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/sourmash/cli/sig/split.py	100.00% <ø> (ø)
src/sourmash/cli/sig/subtract.py	100.00% <ø> (ø)
src/sourmash/cli/sketch/__init__.py	100.00% <ø> (ø)
src/sourmash/cli/sketch/dna.py	100.00% <ø> (ø)
src/sourmash/cli/sketch/protein.py	100.00% <ø> (ø)
src/sourmash/cli/sketch/translate.py	100.00% <ø> (ø)
src/sourmash/cli/storage/__init__.py	100.00% <ø> (ø)
src/sourmash/cli/storage/convert.py	100.00% <ø> (ø)
src/sourmash/minhash.py	90.62% <100.00%> (+0.70%)	⬆️
src/sourmash/sourmash_args.py	94.24% <0.00%> (-0.18%)	⬇️
... and 68 more

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