fix: check for file presence after download

src/main.rs

@@ -1,4 +1,4 @@
-use std::{error::Error, process::Command};
+use std::{error::Error, fs, process::Command};
 
 use shy_launcher::{config::Config, downloader};
 
@@ -10,6 +10,15 @@ async fn main() -> Result<(), Box<dyn Error>> {
     println!("Starting download...");
     downloader::download(config.downloads()).await;
 
+    println!("Verifying file presence...");
+    for download in config.downloads() {
+        let filename = download.filename();
+        if !fs::exists(filename)? {
+            panic!("Required file {} not present", filename);
+        }
+        println!("[ok] {}", filename);
+    }
+
     println!("Freeing memory...");
     if unsafe { libc::malloc_trim(0) } == 1 {
         println!("Freed up some memory.");