[gtk-web: 1/2] Update sample_codes.yml

[Emmanuele Bassi <ebassi src gnome org>]

commit eab2e355be59ee614a0654125da3cd524656bfdc
Author: Aaron Honeycutt <aaron system76 com>
Date:   Fri Feb 21 16:34:20 2020 +0000

    Update sample_codes.yml

 _data/sample_codes.yml | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/_data/sample_codes.yml b/_data/sample_codes.yml
index 5e000af..27e1e75 100644
--- a/_data/sample_codes.yml
+++ b/_data/sample_codes.yml
@@ -84,6 +84,8 @@ codes:
     ext: vala
     snippet: |
       ```vala
+      using Gtk;
+      
       int main (string[] argv) {
           // Create a new application
           var app = new Gtk.Application ("com.example.GtkApplication",