Node version incompatibility

Node version expectation is too strict:

```
$ yarn
yarn install v1.16.0
[1/5] Validating package.json...
error nextjs-pwa-graphql-sql-boilerplate@1.3.0: The engine "node" is incompatible with this module. Expected version "^10.13.0". Got "12.5.0"
error Found incompatible module.
```