Add feature for cursor and range rings

shaders/ascope_graticule_text.frag

@@ -0,0 +1,9 @@
+#version 330 core
+in vec2 vUV;
+uniform sampler2D uTexture;
+uniform vec3 uColor;
+out vec4 FragColor;
+void main() {
+    float alpha = texture(uTexture, vUV).r;
+    FragColor = vec4(uColor, alpha);
+}