Fixed jlink build

Signed-off-by: PAlex404 <alessandro.parisi406@gmail.com>

.run/MaterialFX [jlinkZip].run.xml

@@ -4,7 +4,7 @@
       <option name="executionName" />
       <option name="externalProjectPath" value="$PROJECT_DIR$" />
       <option name="externalSystemIdString" value="GRADLE" />
-      <option name="scriptParameters" value="" />
+      <option name="scriptParameters" value="-PchooseMain=io.github.palexdev.materialfx.demo.Demo" />
       <option name="taskDescriptions">
         <list />
       </option>

demo/build.gradle

@@ -32,6 +32,7 @@ application {
 jlink {
     imageZip = file("$buildDir/$rootProject.name-$rootProject.version" + '.zip')
     launcher {
+        mainClass = "io.github.palexdev.materialfx.demo.Demo"
         name = 'MaterialFX Demo'
     }
     jpackage {