Reference typings in package.json

[ianks]

This PR allows typescript users to simply npm install reselect to get typings support. For more information on how this works, check out this link: https://github.com/Microsoft/TypeScript/wiki/Typings-for-npm-packages

As a note, I gave @frankwallis the commit authorship, because he wrote the original commits for the typings. He was not involved in this PR, however. Sorry for any confusion!

[codecov-io]

Current coverage is 100.00%

Merging #94 into master will not affect coverage as of 685f8f7

@@            master     #94   diff @@
======================================
  Files            1       1       
  Stmts           42      42       
  Branches         0       0       
  Methods          0       0       
======================================
  Hit             42      42       
  Partial          0       0       
  Missed           0       0       

Review entire Coverage Diff as of 685f8f7

Powered by Codecov. Updated on successful CI builds.

[ellbee]

Thank you!