Initial work on implementing Pokemon

PkmnLib.Static/Utils/EnumerableHelpers.cs

@@ -0,0 +1,7 @@
+namespace PkmnLib.Static.Utils;
+
+public static class EnumerableHelpers
+{
+    public static IEnumerable<T> WhereNotNull<T>(this IEnumerable<T?> enumerable) where T : class =>
+        enumerable.Where(x => x is not null)!;
+}