message: Fix/not update schema
  * fix(graphql-playground-react): not update schema
  Schema isn't updated from the previous one after getting a new graphql schema by introspection query unless headers are set. This commit fixes it.
  * docs(graphql-playground-react): correct types of props
diff: @@ -84,7 +84,7 @@ export interface Props {
  configIsYaml: boolean
  canSaveConfig: boolean
  fixedEndpoints: boolean
  - headers?: any
  + headers?: { [key: string]: string }
  configPath?: string
  createApolloLink?: (
  session: Session,
  @@ -104,7 +104,10 @@ export interface ReduxProps {
  saveConfig: () => void
  saveSettings: () => void
  setTracingSupported: (value: boolean) => void
  - injectHeaders: (headers: string, endpoint: string) => void
  + injectHeaders: (
  + headers: string | { [key: string]: string } | void,
  + endpoint: string,
  + ) => void
  setConfigString: (str: string) => void
  schemaFetchingError: (endpoint: string, error: string) => void
  schemaFetchingSuccess: (
  @@ -258,7 +261,9 @@ export class Playground extends React.PureComponent<Props & ReduxProps, State> {
  headers:
  props.sessionHeaders && props.sessionHeaders.length > 0
  ? props.sessionHeaders
  - : JSON.stringify(props.headers),
  + : props.headers && Object.keys(props.headers).length > 0
  + ? JSON.stringify(props.headers)
  + : undefined,
  credentials: props.settings['request.credentials'],
  useTracingHeader:
  !this.initialSchemaFetch &&
  