GH-237 - Core starter now references the Spring Boot Starter explicitly.

As recommended in the Spring Boot reference documentation [0].

[0] https://docs.spring.io/spring-boot/docs/current/reference/htmlsingle/#features.developing-auto-configuration.custom-starter.starter-module

spring-modulith-starters/spring-modulith-starter-core/pom.xml

@@ -41,6 +41,11 @@
 			<scope>runtime</scope>
 		</dependency>
 
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter</artifactId>
+		</dependency>
+
 	</dependencies>
 
 </project>