add debian sid to travis-CI config

.docker.json

@@ -10,6 +10,30 @@
 	  "make",
 	  "mate-common"
     ],
+    "debian" : [
+	  "git",
+	  "gobject-introspection",
+	  "gtk-doc-tools",
+	  "intltool",
+	  "libcanberra-gtk3-dev",
+	  "libdconf-dev",
+	  "libexempi-dev",
+	  "libexif-dev",
+	  "libgail-3-dev",
+	  "libgirepository1.0-dev",
+	  "libglib2.0-dev",
+	  "libgtk-3-dev",
+	  "libmate-desktop-dev",
+	  "libnotify-dev",
+	  "libpango1.0-dev",
+	  "libstartup-notification0-dev",
+	  "libwnck-3-dev",
+	  "libx11-dev",
+	  "libxml2-dev",
+	  "mate-common",
+	  "quilt",
+	  "shared-mime-info"
+    ],
     "fedora" : [
 	  "desktop-file-utils",
 	  "git",

.travis.yml

@@ -14,5 +14,6 @@ script:
 
 env:
   - DISTRO="base/archlinux"
+  - DISTRO="debian:sid"
   - DISTRO="fedora:29"
   - DISTRO="ubuntu:18.10"