Fix extra slash on HEAD request for schema hash (#13)

src/client.ts

@@ -774,7 +774,7 @@ export class CwRqlClient implements RqlClient {
     }
 
     public getSchemaHash(): Promise<string | null> {
-        return fetch(`${this.httpClient.baseUrl}/rqlio/schema/`, {
+        return fetch(`${this.httpClient.baseUrl}rqlio/schema/`, {
             method: 'HEAD',
         }).then(response => {
             const hash = response.headers.get('Etag');