docs(frontend/python): overhaul python frontend docs

docs/getting-started/installing.md

@@ -0,0 +1,21 @@
+# Installation
+
+**Concrete** is natively supported on Linux and macOS from Python 3.8 to 3.10 inclusive, but if you have Docker in your platform, you can use the docker image to use **Concrete**.
+
+## Using PyPI
+
+You can install **Concrete** from PyPI:
+
+```shell
+pip install -U pip wheel setuptools
+pip install concrete-python
+```
+
+## Using Docker
+
+You can also get the **Concrete** docker image:
+
+```shell
+docker pull zamafhe/concrete-python:v1.0.0
+docker run --rm -it zamafhe/concrete-python:latest /bin/bash
+```