docs: adding skeleton README.md files for all vlib modules (#13034)

vlib/gg/README.md

@@ -0,0 +1,35 @@
+## Description:
+
+`gg` is V's simple graphics module.
+It is currently implemented using `sokol`, and makes easy creating
+apps that just need a way to draw simple 2D shapes, and to react to
+user's keyboard/mouse input.
+
+## Example:
+
+```v
+module main
+
+import gg
+import gx
+
+fn main() {
+	mut context := gg.new_context(
+		bg_color: gx.rgb(174, 198, 255)
+		width: 600
+		height: 400
+		window_title: 'Polygons'
+		frame_fn: frame
+	)
+	context.run()
+}
+
+fn frame(mut ctx gg.Context) {
+	ctx.begin()
+	ctx.draw_convex_poly([f32(100.0), 100.0, 200.0, 100.0, 300.0, 200.0, 200.0, 300.0, 100.0, 300.0],
+		gx.blue)
+	ctx.draw_poly_empty([f32(50.0), 50.0, 70.0, 60.0, 90.0, 80.0, 70.0, 110.0], gx.black)
+	ctx.draw_triangle_filled(450, 142, 530, 280, 370, 280, gx.red)
+	ctx.end()
+}
+```