Add plugin-warn-if-update-available plugin

[thinkingserious]

• The plugin currently checks once per day.
• The upgrade message can be updated in the package.json settings.
• The update is triggered upon release to the public npm registry.

Checklist

• I acknowledge that all my contributions will be made under the project's license

[childish-sambino]

Builds are failing.

[codecov]

Codecov Report

Merging #68 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #68   +/-   ##
=======================================
  Coverage   98.76%   98.76%           
=======================================
  Files          26       26           
  Lines         728      728           
=======================================
  Hits          719      719           
  Misses          9        9

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[thinkingserious]

Build fixed, thanks!