Add icon for account theme picker (#619)

Author: janfaracik

pom.xml

@@ -55,7 +55,7 @@
     <dependency>
       <groupId>io.jenkins.plugins</groupId>
       <artifactId>theme-manager</artifactId>
-      <version>294.vf2c2fd783821</version>
+      <version>310.v234c7de84f9c</version>
     </dependency>
 
     <dependency>

src/main/java/io/jenkins/plugins/darktheme/DarkThemeManagerFactory.java

@@ -39,6 +39,11 @@ public String getDisplayName() {
             return "Dark";
         }
 
+        @Override
+        public String getIconClassName() {
+            return "symbol-moon-outline plugin-ionicons-api";
+        }
+
         @NonNull
         @Override
         public String getThemeId() {

src/main/java/io/jenkins/plugins/darktheme/DarkThemeSystemManagerFactory.java

@@ -35,6 +35,11 @@ public String getDisplayName() {
             return "Dark (System)";
         }
 
+        @Override
+        public String getIconClassName() {
+            return "symbol-moon-outline plugin-ionicons-api";
+        }
+
         @NonNull
         @Override
         public String getThemeId() {