add sample module

sample/readme.md

@@ -0,0 +1,16 @@
+# Application modules
+
+This allows for the loading of server-side modules which can, in turn,
+inject browser modules into applications like Kiri:Moto.
+
+To enable the sample module:
+
+* create a `mod` directory at the root of grid-apps
+* copy the sample directory into the mod directory: `mod/sample`
+* (re)start `gs-app-server`
+* you will see log lines at start-up similar to this
+
+```
+220128.120432 '[head]' { module: './mod/sample/init.js' }
+220128.120432 '[head]' '--- sample server-side module loaded ---'
+```