Implement `execute' action keyword

lib/uh/wm/actions_handler.rb

@@ -12,6 +12,21 @@ module Uh
       def quit
         @events.emit :quit
       end
+
+      def execute command
+        @env.log "Execute: #{command}"
+        pid = fork do
+          fork do
+            Process.setsid
+            begin
+              exec command
+            rescue Errno::ENOENT => e
+              @env.log_error "ExecuteError: #{e}"
+            end
+          end
+        end
+        Process.waitpid pid
+      end
     end
   end
 end