add simple slider component

example/kenney/gui/main/main.gui

@@ -1570,6 +1570,69 @@ nodes {
   template_node_child: false
   size_mode: SIZE_MODE_AUTO
 }
+nodes {
+  position {
+    x: 0.0
+    y: 20.0
+    z: 0.0
+    w: 1.0
+  }
+  rotation {
+    x: 0.0
+    y: 0.0
+    z: 0.0
+    w: 1.0
+  }
+  scale {
+    x: 0.7
+    y: 0.7
+    z: 1.0
+    w: 1.0
+  }
+  size {
+    x: 100.0
+    y: 60.0
+    z: 0.0
+    w: 1.0
+  }
+  color {
+    x: 1.0
+    y: 1.0
+    z: 1.0
+    w: 1.0
+  }
+  type: TYPE_TEXT
+  blend_mode: BLEND_MODE_ALPHA
+  text: "50%"
+  font: "game"
+  id: "text_progress_slider"
+  xanchor: XANCHOR_NONE
+  yanchor: YANCHOR_NONE
+  pivot: PIVOT_CENTER
+  outline {
+    x: 0.0
+    y: 0.0
+    z: 0.0
+    w: 1.0
+  }
+  shadow {
+    x: 1.0
+    y: 1.0
+    z: 1.0
+    w: 1.0
+  }
+  adjust_mode: ADJUST_MODE_FIT
+  line_break: false
+  parent: "slider_back"
+  layer: ""
+  inherit_alpha: true
+  alpha: 1.0
+  outline_alpha: 1.0
+  shadow_alpha: 0.0
+  template_node_child: false
+  text_leading: 1.0
+  text_tracking: 0.0
+}
 nodes {
   position {
     x: 0.0