Add infrastructure to check for problems with npm configuration files

[per1234]

A task and GitHub Actions workflow are provided here for checking the project's npm package manager configuration.

On every push and pull request that affects relevant files, and periodically:

• Validate package.json against its JSON schema.
• Check for forgotten package-lock.json syncs.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.05%. Comparing base (cf933a8) to head (aa7676a).
Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #786   +/-   ##
=======================================
  Coverage   90.05%   90.05%           
=======================================
  Files          44       44           
  Lines        6800     6800           
=======================================
  Hits         6124     6124           
  Misses        553      553           
  Partials      123      123           

Flag	Coverage Δ
unit	90.05% <ø> (ø)

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