Add deprecation policy

[vEpiphyte]

No description provided.

[codecov]

Codecov Report

Merging #1895 into master will increase coverage by 2.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1895      +/-   ##
==========================================
+ Coverage   94.44%   96.56%   +2.12%     
==========================================
  Files         139      139              
  Lines       26120    26120              
==========================================
+ Hits        24670    25224     +554     
+ Misses       1450      896     -554     

Flag	Coverage Δ
#linux	96.56% <ø> (+2.12%)	⬆️
#linux_replay	71.05% <ø> (+1.47%)	⬆️

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Impacted Files	Coverage Δ
synapse/lib/ast.py	98.06% <0.00%> (+0.05%)	⬆️
synapse/lib/types.py	97.82% <0.00%> (+0.09%)	⬆️
synapse/lib/layer.py	97.97% <0.00%> (+0.20%)	⬆️
synapse/lib/node.py	97.73% <0.00%> (+0.20%)	⬆️
synapse/cortex.py	95.79% <0.00%> (+0.39%)	⬆️
synapse/lib/stormtypes.py	97.50% <0.00%> (+0.41%)	⬆️
synapse/cryotank.py	91.32% <0.00%> (+0.57%)	⬆️
synapse/common.py	97.14% <0.00%> (+1.26%)	⬆️
synapse/lib/view.py	94.56% <0.00%> (+1.48%)	⬆️
synapse/lib/cli.py	92.13% <0.00%> (+2.24%)	⬆️
... and 14 more

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