Add IsInteger and IsFloat; Fix Integer and Float handing with edge case

[Emiyaaaaa]

fixed: #637

Breaking but I think it's the corrent changes:

type Change1 = Integer<1 | 1.5>
// latest version => never // auther commented: This may be undesired behavior
// this PR        => 1

type Change2 = Integer<1e+100>
// latest version => never
// this PR        => 1e+100 // Number.IsInteger(1e+100) is true

type Change3 = Float<PositiveInfinity>
// latest version => PositiveInfinity
// this PR        => never // Infinity isn't a float.

And clarifies how to deal with some special number type like '1.0', '0x10' and negative number

[Emiyaaaaa]

Should we expose IsFloat and IsInteger? I think these are useful types. @sindresorhus

I can move these into internal.ts first, then add document and expose later or in a new PR.

[sindresorhus]

Yes. I think they are useful too. Up to you whether it's done now or in a later PR.