Include welcome.js in package

[thinkingserious]

The missing welcome.js file is causing installation troubles

Checklist

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

[codecov]

Codecov Report

Merging #39 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master     #39   +/-   ##
======================================
  Coverage    98.4%   98.4%           
======================================
  Files          22      22           
  Lines         565     565           
======================================
  Hits          556     556           
  Misses          9       9

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