Added first script, bugfixes

PkmnLib.Static/Utils/StringKey.cs

@@ -13,6 +13,8 @@ public readonly record struct StringKey
     /// <inheritdoc cref="StringKey"/>
     public StringKey(string key)
     {
+        if (string.IsNullOrWhiteSpace(key))
+            throw new ArgumentException("Key cannot be null or whitespace.", nameof(key));
         _key = key;
     }