fix(loader): loadPlugin can be extended

[popomore]

Checklist

• npm test passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

Description of change

[codecov]

Codecov Report

Merging #836 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master   #836   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files          27     27           
  Lines         666    666           
=====================================
  Hits          666    666

Impacted Files	Coverage Δ
lib/loader/app_worker_loader.js	100% <100%> (ø)	⬆️
lib/loader/agent_worker_loader.js	100% <100%> (ø)	⬆️

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[popomore]

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