Base: Add the serenity-application HackStudio template

This is a template which instantiates into what you'd write to start out
a basic Serenity GUI application. It contains a CMakeLists.txt file
which describes what each declaration does, a simple GUI application
which uses layouts, widgets and callbacks, and comes with a minimal set
of pledges which the user can add to as necessary.

Base/res/devel/templates/serenity-application.postcreate

@@ -0,0 +1,28 @@
+#!/bin/sh
+
+echo > $2/CMakeLists.txt <<-EOF
+# NOTE! Make sure to edit this file and remove the comments before submitting a
+# PR for a new application.
+
+# Defines your application component. If the application is essential to the
+# system's operation, add REQUIRED. If it would be beneficial for the user that
+# this application is built by default, add RECOMMENDED.
+serenity_component(
+    $1
+    TARGETS $1
+)
+
+# Place source files here. You should also add auto-generated headers, if you
+# have any.
+set(SOURCES
+    main.cpp
+)
+
+# Change this to something cool. :^)
+serenity_app($1 ICON filetype-executable)
+
+# You should place all the libraries that your application uses here. You can
+# identify each library by their include path. An exception is LibCore, which
+# is linked to all components by default.
+target_link_libraries($1 LibGUI LibGfx)
+EOF