add babel auto import to jest test section of config

[thedavidprice]

@peterp Continuing the work from #152 which I thought was working when testing locally (I think my yarn lock was keeping packages I had removed).

Previously, I tried to move the auto-import from Webpack to Babel, which worked for Jest but did not work for running the development environment. When I read your recent doc about where/how we build, it seems that Webpack only is how we're building the web/ side, and not our file core/config/babel-preset.js. Researching a bit further about babel, I think I now understand this code:

overrides: [
    // ** API **
    {
      test: './api/',
      presets: [
        [
          '@babel/preset-env',
          {
            targets: {
              node: TARGETS_NODE,
...

and this

 // ** WEB **
    {
      test: './web',
...

is effectively a switch to use the included settings only to transpile in the case Jest is being run.

Am I correct?

If so, the changes in this PR include adding the auto-import to the "Web" section of the babel config file. I've kept the auto-import settings in Webpack.

My local testing confirms the yarn rw test command now runs correctly (and passes) using the updated test templates in master redwood branch, which do not import React and gql implicitly. And the command yarn rw dev also runs as expected with no browser errors.

Are we there? Finally?!?