Document how to hot reload in IntelliJ IDEA

README.md

@@ -146,7 +146,25 @@ $ ./mvnw spring-boot:run
 $ java -jar target/app.jar
 ```
 
-# Appendix: Usage with just
+# Appendix
+
+## Hot reloading during development
+
+In IntelliJ IDEA you can enable hot reloading for the running application with:
+
+- `Settings` > `Build, Execution, Deployment` > `Compiler`:
+  [X] Build project automatically
+- `Settings` > `Advanced Settings`:
+  [X] Allow auto-make to start even if developed application is currently running
+
+With this configured, you don't need to restart the application manually when
+you made code changes. Hot reload will work both when running the application
+via IntelliJ IDEA from the IDE as well as when running the application in a
+terminal with `./mvnw spring-boot:run`.
+
+Note that it can take a few seconds for the refresh to happen.
+
+## Usage with just
 
 If you have [just](https://github.com/casey/just) installed, you can run the
 commands above more conveniently as per this project's [justfile](justfile):