Readme: fix steam deck instructions

Turns out that setting the desktop env isn't enough we also need to 
manually ensure kwalletd is started. As we can't tell steam to run 
multiple commands, people will need a small wrapper script that 
does this.

README.md

@@ -146,9 +146,11 @@ guix install nheko
 
 #### Steam Deck
 
-Install nheko via the `Discover` app in Desktop Mode (this installs the flatpak). To also make it work in Game Mode you'll have to add it as a "Non-Steam Game" to steam and than add the following `--env` variables to the `flatpak run` command. This is necessary for nheko to connect to KWallet correctly. The resulting arguments field in the steam settings should look something like this.
-```
-run --env=XDG_CURRENT_DESKTOP=KDE --env=KDE_SESSION_VERSION=5 --branch=stable --arch=x86_64 --command=io.github.NhekoReborn.Nheko --file-forwarding io.github.NhekoReborn.Nheko @@u @@
+Install nheko via the `Discover` app in Desktop Mode (this installs the flatpak). To also make it work in Game Mode you'll have create a wrapper script that starts kwalletd and then nheko. You can create `/home/deck/nheko.sh` with the following content and then add this script as a "Non-Steam Game" to Steam.
+```bash
+#!/bin/sh
+kwalletd5&
+flatpak run --env=XDG_CURRENT_DESKTOP=KDE --env=KDE_SESSION_VERSION=5 --branch=stable --arch=x86_64 --command=io.github.NhekoReborn.Nheko --file-forwarding io.github.NhekoReborn.Nheko @@u @@
 ```
 
 #### macOS (10.14 and above)