Add webapp doc (#652)

docs/webapp.md

@@ -0,0 +1,42 @@
+### Building and Running Webapps
+
+It is possible to build and run webapps using the `build-webapp` and `run-webapp` subcommand.
+
+To make it easier to build once, and deploy to with varying configuration, compilation and static
+page generation are separated in the `build-webapp` and `run-webapp` steps, and the use of the
+environment variables via `process.env` is detected at compile-time and placeholder substituted
+which will be filled in at runtime.
+
+This offers much more flexibilty in configuration and deployment than standard build methods.
+
+## Build
+
+```
+$ cd ~/cerc
+$ git clone [email protected]:cerc-io/test-progressive-web-app.git
+$ laconic-so build-webapp --source-repo ~/cerc/test-progressive-web-app
+...
+Successfully tagged cerc/test-progressive-web-app:local
+
+
+#################################################################
+
+Built host container for ~/cerc/test-progressive-web-app with tag:
+
+    cerc/test-progressive-web-app:local
+
+To test locally run:
+
+    laconic-so run-webapp --image cerc/test-progressive-web-app:local --env-file /path/to/environment.env
+
+```
+
+## Run
+
+```
+$ laconic-so run-webapp --image cerc/test-progressive-web-app:local --env-file ~/tmp/env.igloo
+
+Image: cerc/test-progressive-web-app:local
+ID: 4c6e893bf436b3e91a2b92ce37e30e499685131705700bd92a90d2eb14eefd05
+URL: http://localhost:32768
+```