update to vue-cli 3

[EmilyRosina]

Plus...

• updated all packages
• updated a few bits of code to work a bit more efficiently
• reworked vuex using mapVuex helpers
• some style changes to keep avatar fixed when scrolling
• convert actions to use async/await instead of .then
• uppercased mutations and actions
• adopted into airbnb eslint 📿 🙇‍♀️
• move repo object out into assets/data
• rework global components, plugins etc to share same syntax
  • but split between vendor and custom directories
  • everything is now regisered through plugins
• fix some linting errors
• improve code with destructring in some places
• register scss vars file using new vue-cli file setup
• register aliases again, using new vue-cli file setup
• switched from github pages to netlify 💪

Helpful to solve build problems

• npm run serve error: You must pass the "decoratorsLegacy": true option to @babel/preset-stage-2 vuejs/vue-cli#1162