message: fix: reexport Symbol.observable typings patch
diff: export { Observable } from './internal/Observable';
  export { ConnectableObservable } from './internal/observable/ConnectableObservable';
  export { Operator } from './internal/Operator';
  +export { observable } from './internal/symbol/observable';
  /* Subjects */
  export { Subject } from './internal/Subject';
  