create a wwwdev.sh entry point for helping live web design/development (#92)

* create a wwwdev.sh entry point for developing the web part

* rename script

* fix README

* add a note

* don't depend on deltachat python package

* avoid bailing out on jinja2 errors, and provide file-url for instant clickability

* in webdev mode make page auto-refresh every 3 seconds

README.md

@@ -51,6 +51,28 @@ The `deploy.sh` script deploys
 All files are generated by the according markdown `.md` file in the `www` directory.
 
 
+### Refining the web pages 
+
+The `scripts/webdev.sh` script supports live development of the chatmail web presence:
+
+``` 
+    scripts/init.sh  # to locally initialize python virtual environments etc. 
+    scripts/webdev.sh
+```
+
+- uses the `www/src/page-layout.html` file for producing html documents
+  from `www/src/*.md` files. 
+
+- continously builds the web presence reading files from `www/src` directory
+  and generating html files and copying assets to the `www/build` directory. 
+
+- Starts a browser window automatically where you can "refresh" as needed. 
+
+Note that this script is not needed for running `scripts/deploy.sh" 
+which deploys the whole chatmail setup remotely. 
+The code that generates the web pages is identical
+which means that `webdev.sh` gives a pretty good preview. 
+
 ### Ports
 
 Postfix listens on ports 25 (smtp) and 587 (submission) and 465 (submissions).