Move config assets to zellij-utils crate

* The assets macro seems to not be able to
read across create boundaries.
Now the assets are included in the crate they are used in.

zellij-utils/assets/README.md

@@ -0,0 +1,4 @@
+# Assets for the Utils Crate
+
+Here reside assets, that are especially needed for
+setup eg. a default configuration file.

zellij-utils/src/setup.rs

@@ -74,7 +74,7 @@ pub fn dump_asset(asset: &[u8]) -> std::io::Result<()> {
 pub const DEFAULT_CONFIG: &[u8] = include_bytes!(concat!(
     env!("CARGO_MANIFEST_DIR"),
     "/",
-    "../assets/config/default.yaml"
+    "assets/config/default.yaml"
 ));
 
 pub fn dump_default_config() -> std::io::Result<()> {