Version 1.6.3

Minor updates to h, createVNode and patch functions.

1. Simplified childNodes assignment in h function.
2. Removed unnecessary parameter in createVNode call.
3. createVNode now has default values of null for key and flag parameters.
4. Updated tests to reflect changes in h function.
5. Instead of assigning default value to createVNode function inside its body, moved assignment as default value in the call signature itself.
6. Marked flag parameter as optional.