@inboxsdk/core should not inline various libraries

[wegry]

@inboxsdk/core should use something like webpack's externals. For widely used libraries like lodash, using the importing project's library versions allows updates, code sharing, and future tooling improvements (in the vein of #905) to occur down the line.

We have a a number of libraries that are currently being inlined.

[
          '@babel/runtime',
          '@macil/simple-base-converter',
          'asap',
          'auto-html',
          'bignumber.js',
          'bimapcache',
          'buffer',
          'classnames',
          'closest-ng',
          'combokeys-capture',
          'contain-by-screen',
          'ext-corb-workaround',
          'fast-deep-equal',
          'immutability-helper',
          'kefir',
          'kefir-bus',
          'kefir-cast',
          'kefir-stopper',
          'live-set',
          'lodash',
          'map-indexed-xf',
          'matches-selector-ng',
          'order-manager',
          'page-parser-tree',
          'pdelay',
          'querystring-es3',
          'react',
          'react-dom',
          'react-draggable-list',
          'react-smooth-collapse',
          'sha.js',
          'ud',
          'ud-kefir',
          'tag-tree',
          'transducers.js',
      ]

Drawbacks

#785 support. Externals make packaging code for users wanting to avoid bundlers trickier.