Add support for material icons on launcher (#521)

- Add support for using material icons on launcher items (for plugins)
- Allow plugins to omit icons
- Update plugin docs
- add developer note so the next one working on launcher will not spend
  hours debugging the wrong place as I just did :)

PLUGINS/LauncherExample/LauncherExampleLauncher.qml

@@ -26,35 +26,35 @@ Item {
         const baseItems = [
             {
                 name: "Test Item 1",
-                icon: "lightbulb",
+                icon: "material:lightbulb",
                 comment: "This is a test item that shows a toast notification",
                 action: "toast:Test Item 1 executed!",
                 categories: ["LauncherExample"]
             },
             {
-                name: "Test Item 2", 
-                icon: "star",
+                name: "Test Item 2",
+                icon: "material:star",
                 comment: "Another test item with different action",
                 action: "toast:Test Item 2 clicked!",
                 categories: ["LauncherExample"]
             },
             {
                 name: "Test Item 3",
-                icon: "favorite",
+                icon: "material:favorite",
                 comment: "Third test item for demonstration",
                 action: "toast:Test Item 3 activated!",
                 categories: ["LauncherExample"]
             },
             {
                 name: "Example Copy Action",
-                icon: "content_copy",
+                icon: "material:content_copy",
                 comment: "Demonstrates copying text to clipboard",
                 action: "copy:This text was copied by the launcher plugin!",
                 categories: ["LauncherExample"]
             },
             {
                 name: "Example Script Action",
-                icon: "terminal",
+                icon: "material:terminal",
                 comment: "Demonstrates running a simple command",
                 action: "script:echo 'Hello from launcher plugin!'",
                 categories: ["LauncherExample"]

PLUGINS/LauncherExample/README.md

@@ -88,13 +88,41 @@ function executeItem(item): void
 ```javascript
 {
     name: "Item Name",           // Display name
-    icon: "icon_name",           // Material icon
+    icon: "icon_name",           // Icon (optional, see Icon Types below)
     comment: "Description",      // Subtitle text
     action: "type:data",         // Action to execute
     categories: ["PluginName"]   // Category array
 }
 ```
 
+**Icon Types**:
+
+The `icon` field supports three formats:
+
+1. **Material Design Icons** - Use `material:` prefix:
+   ```javascript
+   icon: "material:lightbulb"  // Material Symbols Rounded font
+   ```
+   Examples: `material:star`, `material:favorite`, `material:settings`
+
+2. **Desktop Theme Icons** - Use icon name directly:
+   ```javascript
+   icon: "firefox"  // Uses system icon theme
+   ```
+   Examples: `firefox`, `chrome`, `folder`, `text-editor`
+
+3. **No Icon** - Omit the `icon` field entirely:
+   ```javascript
+   {
+       name: "😀  Grinning Face",
+       // No icon field
+       comment: "Copy emoji",
+       action: "copy:😀",
+       categories: ["MyPlugin"]
+   }
+   ```
+   Perfect for emoji pickers or text-only items where the icon area should be hidden
+
 **Action Format**: `type:data` where:
 - `type` - Action handler (toast, copy, script, etc.)
 - `data` - Action-specific data