add yaru theme

unite@hardpixel.eu/schemas/org.gnome.shell.extensions.unite.gschema.xml

@@ -15,6 +15,7 @@
     <value value="12" nick="pop-dark" />
     <value value="13" nick="pop-light" />
     <value value="14" nick="vimix" />
+    <value value="15" nick="yaru" />
   </enum>
 
   <enum id="org.gnome.shell.extensions.unite.hideTitlebars">

unite@hardpixel.eu/settings.ui

@@ -429,6 +429,7 @@
               <item id="12" translatable="yes">Pop Dark</item>
               <item id="13" translatable="yes">Pop Light</item>
               <item id="14" translatable="yes">Vimix</item>
+              <item id="15" translatable="yes">Yaru</item>
             </items>
           </object>
           <packing>

unite@hardpixel.eu/themes/yaru/stylesheet.css

@@ -0,0 +1,40 @@
+.window-button .icon {
+  width: 24px;
+  height: 24px;
+}
+
+.close .icon {
+  background-image: url("close_focused.svg");
+}
+
+.close:hover .icon {
+  background-image: url("close_focused_prelight.svg");
+}
+
+.close:active .icon {
+  background-image: url("close_focused_pressed.svg");
+}
+
+.minimize .icon {
+  background-image: url("minimize_focused.svg");
+}
+
+.minimize:hover .icon {
+  background-image: url("minimize_focused_prelight.svg");
+}
+
+.minimize:active .icon {
+  background-image: url("minimize_focused_pressed.svg");
+}
+
+.maximize .icon {
+  background-image: url("maximize_focused.svg");
+}
+
+.maximize:hover .icon {
+  background-image: url("maximize_focused_prelight.svg");
+}
+
+.maximize:active .icon {
+  background-image: url("maximize_focused_pressed.svg");
+}