new annotation gutter icons

src/main/java/edu/kit/kastel/highlighter/HighlighterManager.java

@@ -36,6 +36,7 @@
 import com.intellij.ui.JBColor;
 import edu.kit.kastel.extensions.guis.AnnotationsListPanel;
 import edu.kit.kastel.extensions.settings.ArtemisSettingsState;
+import edu.kit.kastel.icons.ArtemisIcons;
 import edu.kit.kastel.sdq.artemis4j.grading.Annotation;
 import edu.kit.kastel.state.PluginState;
 import edu.kit.kastel.utils.EditorUtil;
@@ -178,7 +179,12 @@ public int hashCode() {
 
             @Override
             public @NotNull Icon getIcon() {
-                return AllIcons.Actions.Edit;
+                return switch (annotations.size()) {
+                    case 1 -> ArtemisIcons.AnnotationsGutter1;
+                    case 2 -> ArtemisIcons.AnnotationsGutter2;
+                    case 3 -> ArtemisIcons.AnnotationsGutter3;
+                    default -> ArtemisIcons.AnnotationsGutter4;
+                };
             }
 
             @Override

src/main/java/edu/kit/kastel/icons/ArtemisIcons.java

@@ -0,0 +1,13 @@
+package edu.kit.kastel.icons;
+
+import com.intellij.openapi.util.IconLoader;
+
+import javax.swing.Icon;
+
+// This class follows IntelliJ's code style conventions
+public final class ArtemisIcons {
+    public static final Icon AnnotationsGutter1 = IconLoader.getIcon("/icons/annotation1.svg", ArtemisIcons.class);
+    public static final Icon AnnotationsGutter2 = IconLoader.getIcon("/icons/annotation2.svg", ArtemisIcons.class);
+    public static final Icon AnnotationsGutter3 = IconLoader.getIcon("/icons/annotation3.svg", ArtemisIcons.class);
+    public static final Icon AnnotationsGutter4 = IconLoader.getIcon("/icons/annotation4.svg", ArtemisIcons.class);
+}