rename 'files' to 'io'

src/io/util.hpp

@@ -0,0 +1,16 @@
+#pragma once
+
+#include <string>
+#include <stdexcept>
+
+namespace io {
+    inline bool is_valid_name(std::string_view name) {
+        static std::string illegalChars = "\\/%?!<>:; ";
+        for (char c : illegalChars) {
+            if (name.find(c) != std::string::npos) {
+                return false;
+            }
+        }
+        return !name.empty();
+    }
+}