Add tskit.json_schema

[benjeffery]

Fixes #1956

[codecov]

Codecov Report

Merging #1972 (186bc77) into main (344326c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main    #1972   +/-   ##
=======================================
  Coverage   93.36%   93.36%           
=======================================
  Files          27       27           
  Lines       25557    25557           
  Branches     1114     1114           
=======================================
  Hits        23861    23861           
  Misses       1660     1660           
  Partials       36       36           

Flag	Coverage Δ
c-tests	92.38% <ø> (ø)
lwt-tests	89.05% <ø> (ø)
python-c-tests	72.12% <ø> (ø)
python-tests	98.78% <ø> (ø)

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Impacted Files	Coverage Δ
python/tskit/metadata.py	99.01% <ø> (ø)

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[jeromekelleher]

In #1944 I added MetadataSchema.permissive_json()`` as a class method that returned this instance - what do you think of that?

[benjeffery]

In #1944 I added MetadataSchema.permissive_json()`` as a class method that returned this instance - what do you think of that?

Ah, hadn't gone closely through that PR yet - Seems a more organised place to put it.

[jeromekelleher]

Nice to get this documented for 0.4.0 @benjeffery?

[benjeffery]

@jeromekelleher Fixed up!

[jeromekelleher]

LGTM