Add feature for cursor and range rings

shaders/ascope_graticule.vert

@@ -0,0 +1,6 @@
+#version 330 core
+layout(location = 0) in vec2 aPos;
+uniform float uYOffset;
+void main() {
+    gl_Position = vec4(aPos.x, aPos.y + uYOffset, 0.0, 1.0);
+}