Add PyPI install instructions (#2383)

Author: casey

README.md

@@ -271,6 +271,12 @@ most Windows users.)
       <td><a href=https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/tools/just/default.nix>just</a></td>
       <td><code>nix-env -iA nixpkgs.just</code></td>
     </tr>
+    <tr>
+      <td><a href=https://github.com/pypa/pipx?tab=readme-ov-file#install-pipx>Various</a></td>
+      <td><a href=https://pypi.org/>PyPI</a></td>
+      <td><a href=https://pypi.org/project/rust-just/>rust-just</a></td>
+      <td><code>pipx install rust-just</code></td>
+    </tr>
     <tr>
       <td><a href=https://voidlinux.org>Void Linux</a></td>
       <td><a href=https://wiki.voidlinux.org/XBPS>XBPS</a></td>