docs: add NixOS installation instructions (#1428)

* docs: add NixOS installation instructions

Co-authored-by: Cursor <cursoragent@cursor.com>

* docs: add changelog entry for NixOS installation

* Update news/+nixos-installation.documentation

---------

Co-authored-by: Cursor <cursoragent@cursor.com>
Co-authored-by: Steve Piercy <web@stevepiercy.com>

Author: 3 people

docs/how-to/install.rst

@@ -69,3 +69,12 @@ You can install the `python3-icalendar package <https://packages.fedoraproject.o
 .. code-block:: shell
 
     sudo dnf install python3-icalendar
+
+NixOS
+-----
+
+You can install the icalendar package on NixOS using ``nix-env``:
+
+.. code-block:: shell
+
+    nix-env -iA nixpkgs.python3Packages.icalendar

news/+nixos-installation.documentation

@@ -0,0 +1 @@
+Added NixOS installation instructions to the documentation. @MichaelFehdrau0205