Add a custom website home page with install instructions

This home page includes more detailed installation instructions and uses
more advanced mkdocs features that are not available in the project's
README.

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

docs/index.md

@@ -1 +1,67 @@
---8<-- "README.md"
+# Frequenz Python SDK
+
+## Introduction
+
+The Frequenz Python SDK is a development kit for interacting with the Frequenz development platform.
+
+## Installation
+
+First, you need to make sure you have Python installed (at least version 3.11):
+
+```console
+$ python3 --version
+Python 3.11.4
+```
+
+!!! note
+
+    These instructions assume you are using a [POSIX compatible
+    `sh`](https://pubs.opengroup.org/onlinepubs/9699919799/utilities/sh.html)
+    shell.
+
+If that command doesn't print a version newer than 3.11.0, you'll need to
+[download and install Python](https://www.python.org/downloads/) first.
+
+To install the SDK, you probably want to create a new virtual environment first:
+
+```sh
+mkdir my-sdk-project
+cd my-sdk-project
+python3 -m venv .venv
+. .venv/bin/activate
+```
+
+!!! tip
+
+    Using [`direnv`](https://direnv.net/) can greatly simplify this process as
+    it automates the creation, activation, and deactivation of the virtual
+    environment. The first time you enable `direnv`, the virtual environment
+    will be created, and each time you enter or leave a subdirectory, it will be
+    activated and deactivated, respectively.
+
+    ```sh
+    sudo apt install direnv # if you use Debian/Ubuntu
+    mkdir my-sdk-project
+    cd my-sdk-project
+    echo "layout python python3" > .envrc
+    direnv allow
+    ```
+
+    This will create the virtual environment and activate it automatically for you.
+
+Now you can install the SDK by using `pip`:
+
+```sh
+python3 -m pip install frequenz-sdk
+```
+
+To verify that the installation worked, you can invoke the Python interpreter and
+import the SDK:
+
+```console
+$ python3
+Python 3.11.4 (main, Jun  7 2023, 10:13:09) [GCC 12.2.0] on linux
+Type "help", "copyright", "credits" or "license" for more information.
+>>> import frequenz.sdk
+>>> 
+```