Add not operator helper functions

[vuvanly]

I'm not sure it's helpful or not, but I found out that when I don't use not operator ! the code is more readable. It takes less time to consume the logic of the code.
So basically, when we have a logic like that:

if (! empty($value)) {}

It becomes more readable if we have function like that:

if (notempty($value)) {}

It's the first time I make something like that, so please comment your thought.
https://github.com/vuvanly/not-operators-helpers