actually add vendor folder

vendor/raylib/build.zig

@@ -0,0 +1,7 @@
+const std = @import("std");
+const raylib = @import("src/build.zig");
+
+// This has been tested to work with zig 0.11.0
+pub fn build(b: *std.Build) void {
+    raylib.build(b);
+}