DOC: add installation instructions for release (#38)

Author: martinfleis

Readme.md

@@ -4,9 +4,27 @@
 
 Xvec combines [Xarray](http://xarray.pydata.org) n-D arrays and [shapely 2](https://shapely.readthedocs.io/en/latest/) planar vector geometries to create a support for vector data cubes in Python. See [this post](https://r-spatial.org/r/2022/09/12/vdc.html) by Edzer Pebesma on an introduction of the concept or the introduction of their implementation in Xvec in our [documentation](https://xvec.readthedocs.io/en/latest/intro.html).
 
+## Project status
+
+The project is in the early stage of development and its API may still change.
+
 ## Installing
 
-Xvec is not released yet and can be installed from GitHub.
+You can install Xvec from PyPI using `pip` or from conda-forge using `mamba` or `conda`:
+
+```sh
+pip install xvec
+```
+
+Or (recommended):
+
+```sh
+mamba install xvec -c conda-forge
+```
+
+### Development version
+
+The development version can be installed from GitHub.
 
 ```sh
 pip install git+https://github.com/xarray-contrib/xvec.git