v6.0.0

Update to @typescript-eslint/* v3. See detailed breaking changes at https://github.com/typescript-eslint/typescript-eslint/releases/tag/v3.0.0

The most notable ones are:

• Dropped support for Node version 8
• Dropped support for TypeScript 3.2

Check out the linked issues for more information about added/removed rules:

• @vue/typescript: typescript-eslint/typescript-eslint#1273
• @vue/typescript/recommended: typescript-eslint/typescript-eslint#1423