refactor: eslint setup

[erisu]

Description

• replace eslint dependencies with @cordova/eslint-config
• update eslint config
• eslint corrections

Testing

• npm t

Checklist

• I've run the tests to see all new and existing tests pass

[codecov-io]

Codecov Report

Merging #822 into master will not change coverage.
The diff coverage is 60%.

@@           Coverage Diff           @@
##           master     #822   +/-   ##
=======================================
  Coverage   89.44%   89.44%           
=======================================
  Files          46       46           
  Lines        2150     2150           
=======================================
  Hits         1923     1923           
  Misses        227      227

Impacted Files	Coverage Δ
src/plugman/platform.js	20% <ø> (ø)	⬆️
src/plugman/util/default-engines.js	100% <ø> (ø)	⬆️
src/plugman/fetch.js	86.06% <ø> (ø)	⬆️
src/cordova/restore-util.js	93.95% <ø> (ø)	⬆️
src/plugman/uninstall.js	93.46% <ø> (ø)	⬆️
src/plugman/platform_operation.js	66.66% <0%> (ø)	⬆️
src/cordova/targets.js	19.23% <0%> (ø)	⬆️
src/plugman/create.js	91.42% <0%> (ø)	⬆️
src/cordova/serve.js	100% <100%> (ø)	⬆️
src/cordova/plugin/add.js	98.65% <100%> (ø)	⬆️
... and 3 more

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