Support testing on Windows

[dplewis]

Closes: #819

• Add .gitattributes file to default to LF line ending
• Add cross-env to handle env variables
• Default watch to browser and added the following commands:

npm run watch:node
npm run watch:browser
npm run watch:react-native

@oallouch Can you try out this branch? I believe with watch, test, and integration should be enough to start contributing.

[codecov]

Codecov Report

Merging #820 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #820   +/-   ##
=======================================
  Coverage   92.07%   92.07%           
=======================================
  Files          54       54           
  Lines        4933     4933           
  Branches     1097     1097           
=======================================
  Hits         4542     4542           
  Misses        391      391

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[oallouch]

Test and watch work perfectly.
My lib folder gets updated.
ReadPreference, here I come !

[dplewis]

@oallouch Glad it worked. Will try to get this in the next release.

@acinader How does this look?

[acinader]

looks good!