Flag to skip when evaluates to false

[joente]

Description

We introduced a flag which can skip values when equal to nil. In some cases, it is useful to exclude values when they
just evaluate to false to be even more clean. For example:

set_type('T', {
    name: 'str',
    canBike: '!bool',
});
T{name: 'Alice', canBike: false}.wrap(); 

The above will return

{
   "name": "Alice"
}

As we wrap() and the wrap-prefix flag ! tells to exclude the properties which evaluate to false.

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• Update Test Wrap

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• New and existing unit tests pass locally with my changes