Fix: Test the RTP itself as well

This fixes the problem that the user sometimes passes the configuration
via the commandline. In this case, the "rtp" variable itself is the
configuration file path. With this fix applied, we check this value
before generating the variants and trying them.

libimagrt/src/configuration.rs

@@ -143,6 +143,7 @@ fn fetch_config(rtp: &PathBuf) -> Result<Value> {
     };
 
     vec![
+        vec![rtp.clone()],
         gen_vars(rtp.clone(), variants.clone(), &modifier),
 
         env::var("HOME").map(|home| gen_vars(PathBuf::from(home), variants.clone(), &modifier))