make readme better

Signed-off-by: Xe <me@christine.website>

README.md

@@ -1,3 +1,32 @@
 # taildeck
 
 A bunch of hacks to install Tailscale on a steam deck
+
+## Building
+
+```
+nix build .#image
+```
+
+## Updating
+
+```
+./gen_tarball.sh
+```
+
+## Installing
+
+If you have a steam deck, try this and see if it works:
+
+```
+mkdir -p ~/.local/share/tailscale/steamos
+sudo mkdir -p /etc/extensions
+curl -o ~/.local/share/tailscale/steamos/tailscale_sysext_1.24.2.raw https://xena.greedo.xeserv.us/pkg/ts-sysext/tailscale_sysext_1.24.2.raw
+sudo ln -s ~/.local/share/tailscale/steamos/tailscale_sysext_1.24.2.raw /etc/extensions/tailscale.raw
+sudo systemd-sysext merge
+sudo systemctl enable --now tailscaled.service
+sudo tailscale up --qr
+```
+
+If you see what I'm doing wrong, please [let me
+know](https://pony.social/@cadey).