Add ability to define a strict object shape

[gajus]

A strict object shape would restrict object to only the properties present in the object shape, i.e.

type TypeTest = {
    foo: string
};

const test = (test: TypeTest) => {

};

// This would work
test({
    foo: 'OK'
});

// This would throw an error
test({
    bar: 'NOT OK'
});

Denoting strict shape would require some sort of special syntax, e.g.

type TypeTest = strict<{
    foo: string
}>;

This syntax could be used for more add-ons, e.g.

type TypeTest = somethingElse<strict<{
    foo: string
}>>;

[phpnode]

flow-runtime has {| foo: string |} and $Shape<T>