doc: Update readme to better explain the project

Update the readme and give a better overview of the intention of the
project. The explanation how to install west has been improved.

Signed-off-by: Jonas Remmert <jremmert@gmx.net>

README.rst

@@ -1,23 +1,30 @@
 LwM2M Server
 ============
 
-Update west
-###########
+This repository hosts a framework to build IoT applications using the LwM2M
+protocol. The framework is based on a Leshan LwM2M server and a Django Backend.
+This combination allows to manage low power IoT devices, e.g. running Zephyr OS
+efficiently.
 
-Make sure to configure west to reference the manifest file (west.yml) and
-update all references with::
+The project is described in more detail in the linked GitHub pages. The
+framework is work in progress and is not yet ready for production use.
 
-  $ west update
-
-Build and Flash the Firmware
-############################
+External Dependencies
+#####################
 
-Build and flash the firmware application with::
+External components are maintained in their respective versions via a `west`
+manifest file. Make sure to configure west to reference the manifest file
+(west.yml) in this repository and update all references with::
 
-  $ west build app -p
-  $ west flash
+  # Initialize this repository and external components in a new workspace
+  $ pip3 install west
+  $ west init -m https://github.com/jonas-rem/lwm2m_server --mr main my_workspace
+  $ cd my-workspace
+  $ west update
 
-Documentation
-#############
+Testing the Framework locally
+#############################
 
-See Sphinx documentation in the linked github pages for a more details.
+The framework can be started locally using docker-compose. By using simulated
+Zephyr device running in the same local environment, it can be easily tested.
+Please check the documentation for more details.