feat: port loaderContext's getOptions from webpack

[qnighy]

This PR contains a:

• bugfix
• new feature
• code refactor
• test update
• typo fix
• metadata update

Motivation / Use-Case

To help webpack/thread-loader#106.

webpack/thread-loader#113 will surely fix the issue above, but the PR will create multiple copies of getOptions implementation. webpack/thread-loader#113 (review)

This PR attempts to extract the common part from getOptions to reuse in webpack and thread-loader.

Breaking Changes

No.

Additional Info

This feature may not fit schema-utils' intended scope. I'm adding the feature here because it's a validation-related feature and webpack already depends on schema-utils, but I'm willing to do extra work if there's a better place for the feature.

cc: @alexander-akait

[codecov]

Codecov Report

Merging #123 (5fe159a) into master (2e768a1) will increase coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #123      +/-   ##
==========================================
+ Coverage   97.57%   97.63%   +0.06%     
==========================================
  Files           6        7       +1     
  Lines         700      720      +20     
  Branches      299      304       +5     
==========================================
+ Hits          683      703      +20     
  Misses         15       15              
  Partials        2        2              

Impacted Files	Coverage Δ
src/getLoaderOptions.js	100.00% <100.00%> (ø)
src/index.js	100.00% <100.00%> (ø)

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[alexander-akait]

We should not put this logic here

[qnighy]

@alexander-akait then where do you think is the best?

[alexander-akait]

Inside thread-loader, we should run webpack API like we do with other loaders methods

[qnighy]

Inside thread-loader, we should run webpack API like we do with other loaders methods

@alexander-akait That seems too difficult to me. Isn't there an option to release webpack/thread-loader#102 without getOptions for the time being? After that I might have a bandwidth for this.

[qnighy]

Closing in favor of webpack/thread-loader#113. Thanks!