message: documentation - added typing to Effects declaration
diff: @@ -57,7 +57,7 @@ API endpoints (so called: `Effects`), middlewares and error handlers (see next c
  The simplest implementation of API endpoint can look like this:
  ```javascript
  -const endpoint$ = request$ => request$
  +const endpoint$: Effect = request$ => request$
  .pipe(
  mapTo({ body: `Hello, world!` })
  );
  @@ -71,7 +71,7 @@ responds with `200` status and `application/json` content type.
  A little bit more complex example can look like this:
  ```javascript
  -const postUser$ = request$ => request$
  +const postUser$: Effect = request$ => request$
  .pipe(
  matchPath('/user'),
  matchType('POST'),
  @@ -91,28 +91,28 @@ which returns a `response` object as an action confirmation.
  Every API requires composable routing. With **Marble.js** routing composition couldn't be easier:
  ```javascript
  -const root$ = request$ => request$
  +const root$: Effect = request$ => request$
  .pipe(
  matchPath('/'),
  matchType('GET'),
  // ...
  );
  -const foo$ = request$ => request$
  +const foo$: Effect = request$ => request$
  .pipe(
  matchPath('/foo'),
  matchType('GET'),
  // ...
  );
  -const getUsers$ = request$ => request$
  +const getUsers$: Effect = request$ => request$
  .pipe(
  matchPath('/'),
  matchType('GET'),
  // ...
  );
  -const postUser$ = request$ => request$
  +const postUser$: Effect = request$ => request$
  .pipe(
  matchPath('/'),
  matchType('POST'),
  @@ -145,7 +145,7 @@ By default framework comes with composable middlewares like: logging, request bo
  Below you can see how easily looks the dummy implementation of API requests logging middleware.
  ```javascript
  -const logger$ = (request$, response) => request$
  +const logger$: Effect<HttpRequest> = (request$, response) => request$
  .pipe(
  tap(req => console.log(`${req.method} ${req.url}`)),
  );
  @@ -173,7 +173,7 @@ Because *Middlewares* and *Effects* are based on the same generic interface, you
  handling middlewares works very similar to normal API *Effects*.
  ```javascript
  -const error$ = (request$, response, error) => request$
  +const error$: Effect<EffectResponse, ThrowedError> = (request$, response, error) => request$
  .pipe(
  map(req => ({
  status: // ...
  