Revert "Remove TextFile from public API"

doc/classes/TextFile.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<class name="TextFile" inherits="Resource" version="4.0">
+	<brief_description>
+	</brief_description>
+	<description>
+	</description>
+	<tutorials>
+	</tutorials>
+	<methods>
+	</methods>
+	<constants>
+	</constants>
+</class>

scene/resources/text_file.h

@@ -36,6 +36,8 @@
 
 class TextFile : public Resource {
 
+	GDCLASS(TextFile, Resource);
+
 private:
 	String text;
 	String path;