Gtk-3.22&3.24&4.0: [Xfce4-panel] Add a workaround for weird notificaton plugin button

Xfce4-panel 4.12.2 specific.
Anyway I saw that Greybird has mysterious L/R 1px padding in button node,
so put the "weird" L/R padding into plugin button.

Close: #726.

gtk/sass/3.22/_3rd-party.scss

diff --git a/gtk/sass/3.22/_3rd-party.scss b/gtk/sass/3.22/_3rd-party.scss
index 35627ad..aee3de7 100644
--- a/gtk/sass/3.22/_3rd-party.scss
+++ b/gtk/sass/3.22/_3rd-party.scss
@@ -2395,6 +2395,10 @@
         box-shadow: none;
       }
     }
+
+    &#xfce4-notification-plugin {
+      padding: 0 1px; // for 4.12.2
+    }
   }
 
   menu {

gtk/sass/3.24/_3rd-party.scss

diff --git a/gtk/sass/3.24/_3rd-party.scss b/gtk/sass/3.24/_3rd-party.scss
index 483eda8..d556546 100644
--- a/gtk/sass/3.24/_3rd-party.scss
+++ b/gtk/sass/3.24/_3rd-party.scss
@@ -2395,6 +2395,10 @@
         box-shadow: none;
       }
     }
+
+    &#xfce4-notification-plugin {
+      padding: 0 1px; // for 4.12.2
+    }
   }
 
   menu {

gtk/sass/4.0/_3rd-party.scss

diff --git a/gtk/sass/4.0/_3rd-party.scss b/gtk/sass/4.0/_3rd-party.scss
index 862bdc5..54676a7 100644
--- a/gtk/sass/4.0/_3rd-party.scss
+++ b/gtk/sass/4.0/_3rd-party.scss
@@ -2374,6 +2374,10 @@
         box-shadow: none;
       }
     }
+
+    &#xfce4-notification-plugin {
+      padding: 0 1px; // for 4.12.2
+    }
   }
 
   menu {