Remote schema SDL filed are not supported.

## Actual Behavior

This extension does not work with remote schemas in graphql-config. i.e. http://somedomain.com/schema.gql
graphql-config supports that.

## Expected Behavior
Extension should support remote schema fetching.

## Steps to Reproduce the Problem Or Description
```
{
schema: "https://someurl.com/schema.gql",
}
```

## Specifications

- GraphQL for VSCode Extension Version: 0.34.1
- VSCode Version: 1.63.0
- OS Name: MacOS
- OS Version: 12.0.1
- graphql config filename and format example:
```
{
schema: "http://someurl.com/schema.gql",
}
```

## Logs Of TS Server || GraphQL Language Service