fix(types): Property 'All' is optional but undefined not allowed

[Tobi-mmt]

This resolves #69

This type is not useful because it says something like:

The key has to be a string, but can also be "All"

But All is a string!

But All can be undefined

So not all strings can be undefined, only All why?

But a key with a string as type can only be boolean, not undefined

That means :

// allowed
{ }
{ All: undefined }
{ All: true }
{ All: false }
{ hotjar: true }
{ hotjar: false }

// NOT allowed
{ hotjar: undefined }

Since this does not make sense and TS is also saying this 2 rules can not match each other we have to change the Type.

With this PR I introduce the new types by removing the All rule. So now we can pass in all strings, also the string All but the values can only be true or false. If you don't want to pass the All key, just do not pass it in the integrations object.
So now the following is the case:

// allowed
{ }
{ All: true }
{ All: false }
{ hotjar: true }
{ hotjar: false }

// NOT allowed
{ All: undefined } // this one changed in this PR
{ hotjar: undefined }

[Tobi-mmt]

@dk1027 @danieljackins @juliofarah can you have a look on that?