improved code in general

build.rs

@@ -0,0 +1,16 @@
+use std::env;
+use std::fs;
+use std::path::Path;
+
+fn main() {
+    println!("cargo:rerun-if-changed=web/dist");
+
+    if env::var_os("CARGO_FEATURE_EMBED_WEB").is_none() {
+        return;
+    }
+
+    let dist_dir = Path::new("web/dist");
+    if let Err(err) = fs::create_dir_all(dist_dir) {
+        panic!("failed to create web/dist for embed-web feature: {err}");
+    }
+}