Fix several texture/shader exercises to use updated code viewer.

src/1.getting_started/3.4.shaders_exercise1/shaders_exercise1.cpp

@@ -0,0 +1,11 @@
+#version 330 core
+layout (location = 0) in vec3 aPos;
+layout (location = 1) in vec3 aColor;
+
+out vec3 ourColor;
+
+void main()
+{
+    gl_Position = vec4(aPos.x, -aPos.y, aPos.z, 1.0); // just add a - to the y position
+    ourColor = aColor;
+}