Add .sdkmanrc for easy Java and Maven version management (OpenAPITools#18552)

* Add .sdkmanrc for easy Java and Maven version management

https://sdkman.io/

* Bump required Maven version for building to 3.8.8

Author: Philzen

.sdkmanrc

@@ -0,0 +1,2 @@
+java=11.0.23-tem
+maven=3.8.8

README.md

@@ -260,7 +260,7 @@ To build from source, you need the following installed and available in your `$P
 
 * [Java 11](https://adoptium.net/)
 
-* [Apache Maven 3.3.4 or greater](https://maven.apache.org/) (optional)
+* [Apache Maven 3.8.8 or greater](https://maven.apache.org/) (optional)
 
 After cloning the project, you can build it from source using [maven wrapper](https://maven.apache.org/wrapper/):