docs: ector_cairo: fill gaps in ector cairo backend eo file documentation

src/lib/ector/cairo/ector_cairo_surface.eo

@@ -19,9 +19,10 @@ class Ector.Cairo.Surface (Efl.Object, Ector.Surface)
 	 }
       }
       symbol_get {
-         return: void_ptr @warn_unused;
+	[[Lookup symbal name in cairo lib]]
+         return: void_ptr @warn_unused; [[Pointer to cairo lib with this symbol]]
          params {
-            @in name: string;
+            @in name: string; [[Symbol name]]
          }
       }
    }

src/lib/ector/cairo/ector_renderer_cairo.eo

@@ -1,10 +1,12 @@
 abstract Ector.Renderer.Cairo (Ector.Renderer)
 {
+   [[Ector cairo renderer abstract class]]
    methods {
       fill @virtual_pure {
-         return: bool;
+      	 [[Fill operation]]
+         return: bool; [[$true on success, $false otherwise]]
          params {
-            @in mul_col: uint;
+            @in mul_col: uint; [[Premultiplied color]]
          }
       }
    }

src/lib/ector/cairo/ector_renderer_cairo_gradient_linear.eo

@@ -1,5 +1,6 @@
 class Ector.Renderer.Cairo.Gradient.Linear (Ector.Renderer.Cairo, Ector.Renderer.Gradient, Ector.Renderer.Gradient.Linear)
 {
+   [[Ector cairo renderer gradient linear]]
    eo_prefix: ector_renderer_cairo_gradient_linear;
    implements {
       Ector.Renderer.prepare;

src/lib/ector/cairo/ector_renderer_cairo_gradient_radial.eo

@@ -1,5 +1,6 @@
 class Ector.Renderer.Cairo.Gradient.Radial (Ector.Renderer.Cairo, Ector.Renderer.Gradient, Ector.Renderer.Gradient.Radial)
 {
+   [[Ector cairo renderer gradient radial]]
    eo_prefix: ector_renderer_cairo_gradient_radial;
    implements {
       Ector.Renderer.prepare;

src/lib/ector/cairo/ector_renderer_cairo_shape.eo

@@ -1,5 +1,6 @@
 class Ector.Renderer.Cairo.Shape (Ector.Renderer.Cairo, Ector.Renderer.Shape)
 {
+   [[Ector cairo renderer shape class]]
    eo_prefix: ector_renderer_cairo_shape;
    implements {
       Ector.Renderer.prepare;