Update references to @rollup/plugin-json

[cprecioso]

In README, docs/, and error messages in test/

This PR contains:

• bugfix
• feature
• refactor
• documentation
• other

Are tests included?

• yes (bugfixes and features will not be merged without tests)
• no

Breaking Changes?

• yes (breaking changes will not be merged unless absolutely necessary)
• no

List any relevant issue numbers:

Description

Update references to rollup-plugin-json throughout documentation and in test files messages. (Expands on #3296)

[codecov]

Codecov Report

Merging #3297 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #3297   +/-   ##
=======================================
  Coverage   93.12%   93.12%           
=======================================
  Files         170      170           
  Lines        5967     5967           
  Branches     1780     1780           
=======================================
  Hits         5557     5557           
  Misses        219      219           
  Partials      191      191

Impacted Files	Coverage Δ
src/Module.ts	97.3% <100%> (ø)	⬆️

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[lukastaegert]

Thanks!