[WIP] Add gatsby-plugin-i18n plugin

[mccrodp]

Attempt to add the gatsby-plugin-i18n plugin...

This gives build errors at the moment on running gatsby develop:

success delete html files from previous builds — 0.008 s
success open and validate gatsby-config.js — 0.004 s
success copy gatsby files — 0.054 s
success onPreBootstrap — 0.009 s
⠁ Starting to fetch data from Contentful
Fetching default locale
⠄ source and transform nodesdefault local is : en-US
⠠ source and transform nodescontentTypes fetched 4
Updated entries  10
Deleted entries  0
Updated assets  11
Deleted assets  0
Fetch Contentful data: 334.602ms
error UNHANDLED EXCEPTION


  TypeError: Cannot read property 'langKey' of undefined

  - onCreateNode.js:49 Object.onCreateNode
    [gatsby-contentful-i18n]/[gatsby-plugin-i18n]/onCreateNode.js:49:25

I presume this is because the Gatsby plugin has en rather than en-US set, but not sure where is throwing the error. Perhaps I could just duplicate the locale related files to use en-US and de like the Contentful example. Will try that next.

[mccrodp]

Tried to play around with file naming and imports re the en-US and de lang codes used in the Contentful example, but no luck there, same error as above. Done for today.

[mccrodp]

Got this working by starting afresh.