fix(acp): max-height for plugin menu list

public/less/admin/header.less

@@ -112,4 +112,9 @@
 			}
 		}
 	}
+
+	.plugins-menu {
+		max-height: 50vh;
+    	overflow-y: auto;
+	}
 }

src/views/admin/partials/menu.tpl

@@ -249,7 +249,7 @@
 			<!-- IF plugins.length -->
 			<li class="dropdown menu-item">
 				<a href="#" class="dropdown-toggle" data-toggle="dropdown" role="button" aria-expanded="false">[[admin/menu:section-plugins]]</a>
-				<ul class="dropdown-menu" role="menu">
+				<ul class="dropdown-menu plugins-menu" role="menu">
 					<li class="dropdown-header">[[admin/menu:section-plugins]]</li>
 					<!-- BEGIN plugins -->
 					<li>