Tech ENABLE_GL_SHADERS_ATTRIBUTES - Added shaders for glsl version 140

(cherry picked from commit prusa3d/PrusaSlicer@76d1d4949b)

resources/shaders/140/imgui.vs

@@ -0,0 +1,17 @@
+#version 140
+
+uniform mat4 ProjMtx;
+
+in vec2 Position;
+in vec2 UV;
+in vec4 Color;
+
+out vec2 Frag_UV;
+out vec4 Frag_Color;
+
+void main()
+{
+	Frag_UV = UV;
+	Frag_Color = Color;
+    gl_Position = ProjMtx * vec4(Position.xy, 0.0, 1.0);
+}