Add src folder back to app project

Author: fipro78

org.fipro.eclipse.tutorial.app/.classpath

@@ -1,10 +1,11 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <classpath>
-	<classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-17">
-		<attributes>
-			<attribute name="module" value="true"/>
-		</attributes>
-	</classpathentry>
-	<classpathentry kind="con" path="org.eclipse.pde.core.requiredPlugins"/>
-	<classpathentry kind="output" path="bin"/>
-</classpath>
+    <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-17">
+        <attributes>
+            <attribute name="module" value="true"/>
+        </attributes>
+    </classpathentry>
+    <classpathentry kind="con" path="org.eclipse.pde.core.requiredPlugins"/>
+    <classpathentry kind="src" path="src"/>
+    <classpathentry kind="output" path="bin"/>
+</classpath>

org.fipro.eclipse.tutorial.app/build.properties

@@ -2,4 +2,7 @@ bin.includes = META-INF/,\
                .,\
                plugin.xml,\
                Application.e4xmi,\
-               css/default.css
+               css/default.css,\
+               src/
+source.. = src/
+output.. = bin/

org.fipro.eclipse.tutorial.app/src/README.md

@@ -0,0 +1 @@
+This is just a placeholder file to have the empty src folder in the repository, so the build does not fail. There will be source files in this folder in later recipes.