Add README files to GUI demos

gui/drag_and_drop/README.md

@@ -0,0 +1,14 @@
+# Drag and Drop (GUI)
+
+A demo showcasing drag and drop functionality.
+
+- Drag and drop the color buttons to copy their colors over.
+- Click on the buttons to manually adjust their color.
+
+Language: GDScript
+
+Renderer: GLES 2
+
+## Screenshots
+
+![Screenshot](screenshots/drag_and_drop.png)

gui/input_mapping/README.md

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+# GUI Input Mapping
+
+A demo showing how to build an input key remapping screen.
+
+- Click the buttons to change the bound keys.
+- Persists the keys to disk, so they are preserved
+  after the project is restarted.
+
+Language: GDScript
+
+Renderer: GLES 2
+
+## Screenshots
+
+![Screenshot](screenshots/input_mapping.png)

gui/rich_text_bbcode/README.md

@@ -0,0 +1,12 @@
+# Rich Text Label with BBCode
+
+A demo showcasing the support for rich text and BBCode via
+[`RichTextLabel`](https://docs.godotengine.org/en/latest/classes/class_richtextlabel.html).
+
+Language: GDScript
+
+Renderer: GLES 2
+
+## Screenshots
+
+![Screenshot](screenshots/rich_text.png)

gui/rich_text_bbcode/project.godot

@@ -15,7 +15,7 @@ _global_script_class_icons={
 
 [application]
 
-config/name="Rich Text Label (BBCode)"
+config/name="Rich Text Label with BBCode"
 run/main_scene="res://rich_text_bbcode.tscn"
 config/icon="res://icon.png"
 

gui/translation/README.md

@@ -0,0 +1,11 @@
+# GUI Translation Demo
+
+A demo showing how Godot seamlessly enables the use of localized resources and texts.
+
+Language: GDScript
+
+Renderer: GLES 2
+
+## Screenshots
+
+![Screenshot](screenshots/translation.png)