update landing page to include install steps

docs/index.rst

@@ -7,25 +7,64 @@
 
 `zk` is a plain text note-taking tool that leverages the power of the command line. 
 
+Install as below and then... :doc:`get zettling <tips/getting-started>`!
+
 Installation
 ============
 
-Mac:
+Homebrew:
 
 .. code-block:: sh
    
-   $ brew install zk
+   brew install zk
+
+   # Or, if you want to be on the bleeding edge:
+   brew install --HEAD zk
+
 
-Or, if you want to be on the bleeding edge:
+Nix:
 
 .. code-block:: sh
 
-   $ brew install --HEAD zk
+   # Run zk from Nix store without installing it:
+   nix run nixpkgs#zk
+
+   # Or, to install it permanently:
+   nix-env -iA zk
+
+Alpine Linux:
+
+.. code-block:: sh
+
+   # `zk` is currently available in the `testing` repositories:
+   apk add zk
+
+Arch Linux:
+
+You can install [the zk package](https://archlinux.org/packages/extra/x86_64/zk/) from the official repos.
+
+.. code-block:: sh
+
+   sudo pacman -S zk
+
+Build from scratch:
+
+Make sure you have a working [Go 1.21+ installation](https://golang.org/), then clone the repository:
+
+.. code-block:: sh
+
+   git clone https://github.com/zk-org/zk.git
+   cd zk
+
+On macOS / Linux:
+
+.. code-block:: sh
 
+   make
+   ./zk -h
 
 
 
-Let's :doc:`get started <tips/getting-started>`.
 
 .. toctree::
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