Add JSON Schema for Config

[fcollonval]

Add a JSON schema for allowed config options and use it to validate user options.

[codecov-commenter]

Codecov Report

Merging #134 (30a6b78) into master (21477d9) will increase coverage by 0.08%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #134      +/-   ##
==========================================
+ Coverage   85.44%   85.53%   +0.08%     
==========================================
  Files          17       17              
  Lines        2096     2101       +5     
  Branches      253      252       -1     
==========================================
+ Hits         1791     1797       +6     
  Misses        213      213              
+ Partials       92       91       -1     

Impacted Files	Coverage Δ
jupyter_releaser/util.py	69.31% <100.00%> (+1.37%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 21477d9...30a6b78. Read the comment docs.

[jtpio]

Thanks!

[jtpio]

Wondering whether this breaks existing repos that have both a pyproject.toml and package.json file? Previously both files would be checked for the configuration, while this doesn't seem to be the case anymore.

This is for example the case in retrolab or the JupyterLab extension cookiecutter:

• https://github.com/jupyterlab/extension-cookiecutter-ts/blob/3ec170c6c40602d509c98fc6fad46e7267beef60/%7B%7Bcookiecutter.python_name%7D%7D/package.json#L88-L95
• https://github.com/jupyterlab/retrolab/blob/9e534b81be7b71218c105e199bea8e90ea2e383b/package.json#L74-L84

[jtpio]

Probably we should keep the previous behavior of cascading through the files to be able to pick up the config.

[jtpio]

Noticed as the check release workflow started to fail here: https://github.com/jupyterlab/retrolab/runs/3535195754

Which seems to be related to the hooks not being run.