Use maven-exec-plugin to simplify execution workflow

Just run `mvn package` to compile & run

pom.xml

@@ -10,20 +10,27 @@
   <build>
     <plugins>
       <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-jar-plugin</artifactId>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>exec-maven-plugin</artifactId>
+        <version>3.1.0</version>
+        <executions>
+          <execution>
+            <phase>package</phase>
+            <goals>
+              <goal>java</goal>
+            </goals>
+          </execution>
+        </executions>
         <configuration>
-                    <archive>
-                        <manifestFile>src/main/resources/META-INF/MANIFEST.MF</manifestFile>
-                    </archive>
+          <mainClass>de.fossag.Main</mainClass>
         </configuration>
       </plugin>
     </plugins>
   </build>
 
   <properties>
-        <maven.compiler.source>20</maven.compiler.source>
-        <maven.compiler.target>20</maven.compiler.target>
+    <maven.compiler.source>17</maven.compiler.source>
+    <maven.compiler.target>17</maven.compiler.target>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <exec.mainClass>de.fossag.Main</exec.mainClass>
   </properties>