refactor: remove __PRODUCTION__ and invariant; add tests for development environment

[angeloashmore]

Types of changes

• Chore (a non-breaking change which is related to package maintenance)
• Bug fix (a non-breaking change which fixes an issue)
• New feature (a non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

This PR refactors the codebase by:

• Replcing __PRODUCTION__ with direct access to process.env.NODE_ENV
• Adds tests for the development environment

Checklist:

• My change requires an update to the official documentation.
• All TSDoc comments are up-to-date and new ones have been added where necessary.
• All new and existing tests are passing.

[codecov-commenter]

Codecov Report

Merging #180 (2da0d38) into master (aac1cc7) will increase coverage by 0.19%.
The diff coverage is 88.23%.

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@@            Coverage Diff             @@
##           master     #180      +/-   ##
==========================================
+ Coverage   99.24%   99.44%   +0.19%     
==========================================
  Files          21       20       -1     
  Lines        2388     2332      -56     
  Branches      129      126       -3     
==========================================
- Hits         2370     2319      -51     
+ Misses         18       13       -5     

Impacted Files	Coverage Δ
src/lib/processPolyfill.ts	25.00% <25.00%> (ø)
src/SliceZone.tsx	98.57% <95.00%> (+0.96%)	⬆️
src/PrismicImage.tsx	100.00% <100.00%> (ø)
src/index.ts	100.00% <100.00%> (ø)
src/react-server/PrismicLink.tsx	100.00% <100.00%> (ø)
src/usePrismicClient.ts	100.00% <100.00%> (ø)

[github-actions]

size-limit report 📦

Path	Size
./dist/index.cjs	6.97 KB (-9.85% 🔽)
./dist/index.js	4.59 KB (-13.39% 🔽)
./dist/react-server.cjs	6.16 KB (-9.99% 🔽)
./dist/react-server.js	4.14 KB (-13.75% 🔽)