doc: Update tricks per tinted-theming schema changes (#792)

The tinted-theming repository has updated its scheme for themes such
that colors are located under the key `palette` [1] and such that each
color is # prefixed [2]. These changes update the documentation to
reflect this new schema.


[1]
4caed9a8f5
[2]
61058a8d2e

docs/src/tricks.md

@@ -33,8 +33,7 @@ Similarly, you can use a template image and repaint it for the current theme.
 let
   theme = "${pkgs.base16-schemes}/share/themes/catppuccin-latte.yaml";
   wallpaper = pkgs.runCommand "image.png" {} ''
-        COLOR=$(${pkgs.yq}/bin/yq -r .base00 ${theme})
-        COLOR="#"$COLOR
+        COLOR=$(${pkgs.yq}/bin/yq -r .palette.base00 ${theme})
         ${pkgs.imagemagick}/bin/magick -size 1920x1080 xc:$COLOR $out
   '';
 in {