fix: add object format support to workspaces field type

[outslept]

The workspaces field was typed as string[] but should support both array and object formats according to the JSON Schema and Yarn Classic conventions.

Resolves #235

P.S. There is an example of using object syntax in an article on nohoist.
UPD2: There's also an RFC to add nohoist to npm, but this isn't implemented for now - npm/rfcs#287

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.22%. Comparing base (afdf7cb) to head (621d361).
Report is 81 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #236      +/-   ##
==========================================
+ Coverage   89.40%   91.22%   +1.82%     
==========================================
  Files           5       10       +5     
  Lines         434      262     -172     
  Branches       37       61      +24     
==========================================
- Hits          388      239     -149     
+ Misses         46       23      -23     

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