title: GraphQLError: Query root type must be provided
body: <p>I'm using NestJS, TypeORM and GraphQL for my backend API. I'm getting the following error:</p>
  <pre><code>GraphQLError [Object]: Query root type must be provided.
        at SchemaValidationContext.reportError (/home/wise-introvert/Container/Projects/the-notebook/app/server/node_modules/graphql/type/validate.js:88:19)
        at validateRootTypes (/home/wise-introvert/Container/Projects/the-notebook/app/server/node_modules/graphql/type/validate.js:107:13)
        at validateSchema (/home/wise-introvert/Container/Projects/the-notebook/app/server/node_modules/graphql/type/validate.js:52:3)
        at graphqlImpl (/home/wise-introvert/Container/Projects/the-notebook/app/server/node_modules/graphql/graphql.js:79:62)
        at /home/wise-introvert/Container/Projects/the-notebook/app/server/node_modules/graphql/graphql.js:28:59
        at new Promise (&lt;anonymous&gt;)
        at Object.graphql (/home/wise-introvert/Container/Projects/the-notebook/app/server/node_modules/graphql/graphql.js:26:10)
        at GraphQLSchemaFactory.&lt;anonymous&gt; (/home/wise-introvert/Container/Projects/the-notebook/app/server/node_modules/@nestjs/graphql/dist/schema-builder/graphql-schema.factory.js:49:52)
        at Generator.next (&lt;anonymous&gt;)
        at /home/wise-introvert/Container/Projects/the-notebook/app/server/node_modules/tslib/tslib.js:114:75
  </code></pre>
  <p>This is what my file structure and code looks like:
  <a href="https://i.stack.imgur.com/fpUEL.png" rel="noreferrer"><img src="https://i.stack.imgur.com/fpUEL.png" alt="enter image description here" /></a></p>
  <p>Can someone please help me. My repo: <a href="https://github.com/wise-introvert/nestjs-graphql-api.git" rel="noreferrer">https://github.com/wise-introvert/nestjs-graphql-api.git</a></p>