title: Rover is composing supergraph with unexpected character
body: <p>I'm following the <a href="https://www.apollographql.com/docs/federation/gateway/#composing-the-supergraph-schema" rel="nofollow noreferrer">docs</a> trying to get an apollo gateway up and running. I'm using rover to compose my subgraph with this command: <code>rover supergraph compose --config ./supergraph-config.yaml &gt; supergraph.graphql</code></p>
  <p>The command works, however when I try to start up my gateway, I get this error: <code>GraphQLError: Syntax Error: Unexpected character: U+FFFD.</code> It seems the supergraph compose command is adding some invalid chatacters for some reason. When I print out the file as a string I see these 2 characters at the top of the file: ��.</p>
  <p>Example:</p>
  <pre><code>��
  schema
    @link(url: &quot;https://specs.apollo.dev/link/v1.0&quot;)
    @link(url: &quot;https://specs.apollo.dev/join/v0.2&quot;, for: EXECUTION)
  {
    query: Query
  }
  ...
  </code></pre>
  <p>I also haven't been able to find any issues on stack overflow or github so I'm not really sure what the issue is.</p>
  <p>Gateway:</p>
  <pre><code>const { ApolloServer, gql } = require('apollo-server');
  const { ApolloGateway } = require('@apollo/gateway');
  const { readFileSync } = require('fs');
  const path = require(&quot;path&quot;);
  
  const schemaString = readFileSync(&quot;../supergraph.graphql&quot;).toString()
  const supergraphSdl = gql` ${schemaString} `;
  
  // Initialize an ApolloGateway instance and pass it
  // the supergraph schema
  const gateway = new ApolloGateway({
    supergraphSdl,
  });
  
  // Pass the ApolloGateway to the ApolloServer constructor
  const server = new ApolloServer({
    gateway,
  });
  
  server.listen().then(() =&gt; {
    console.log(` Gateway ready `);
  });
  </code></pre>
  <p>Subgraph:</p>
  <pre><code>const { ApolloServer, gql } = require('apollo-server');
  const { buildSubgraphSchema } = require('@apollo/subgraph');
  
  interface User {
      id: string
      username: string
  }
  
  const typeDefs = gql`
    extend schema
      @link(url: &quot;https://specs.apollo.dev/federation/v2.0&quot;,
            import: [&quot;@key&quot;, &quot;@shareable&quot;])
  
    type Query {
      me: User
    }
  
    type User @key(fields: &quot;id&quot;) {
      id: ID!
      username: String
    }
  `;
  
  const resolvers = {
    Query: {
      me() {
        return { id: &quot;1&quot;, username: &quot;@ava&quot; }
      }
    },
    User: {
      __resolveReference(user: User, { fetchUserById }: any){
        return fetchUserById(user.id)
      }
    }
  }
  
  const server = new ApolloServer({
    schema: buildSubgraphSchema({ typeDefs, resolvers })
  });
  
  server.listen(3000).then(({ url }) =&gt; {
      console.log(` Server ready at ${url}`);
  });
  </code></pre>