Update README

README.md

@@ -56,7 +56,7 @@
 
   ```ini
   lib_deps =
-    SignalK/SensESP @ >=3.0.0-beta.1,<4
+    SignalK/SensESP @ >=3.0.0-beta.2,<4
     # https://github.com/SignalK/SensESP.git  # Use this line to use the latest git version
     # symlink:///Users/mairas/src/SignalK/SensESP  # Use this line to use a local copy
   ```
@@ -106,6 +106,18 @@
   `reactesp::EventLoop`. In particular, this change probably needs to be made
   in your project's `main.cpp` file.
 
+- `ReactESP` is no longer a singleton. Earlier, you could refer to the singleton
+  instance of `ReactESP` using `ReactESP::app`. Now, the object pointer is
+  maintained by the `SensESPBaseApp` class, and you can refer to it using
+  `sensesp_app->get_event_loop()`. For example:
+
+  ```cpp
+  SensESPBaseApp::get_event_loop()->onRepeat(
+    1000,
+    []() { Serial.println("Hello, world!"); }
+  );
+  ```
+
 ### Development
 
 The frontend project is in the `frontend` directory tree. To build the frontend,