- added babel plugin

- updated axios, core-js, etc
- updated types, test utils, etc
- updated ts config
- added volar config
- changed some imports that gave errors
- removed some "private" modifiers
- added components.d.ts
- deleted shims-tsx.d.ts
- added vue-test-utils-helpers.d.ts
- removed extra Vue.use()
- misc cleanup

babel.config.js

@@ -1,5 +1,6 @@
 module.exports = {
  presets: [
  '@vue/cli-plugin-babel/preset'
- ]
+ ],
+ plugins: ['@babel/plugin-proposal-private-methods']
 }