[cacheable-request] Include type alias for cache adapter (#34155)
[cacheable-request] Include type alias for cache adapter (#34155)

* [cacheable-request] Include type alias for cache adapter

This allows easily declaring a parameter that will be passed into the
constructor.

Ref https://github.com/sindresorhus/got/pull/760#discussion_r268277506

* Fix missing semicolon

* Move StorageAdapter into namespace

georgemarshall/DefinitelyTyped,borisyankov/DefinitelyTyped,markogresak/DefinitelyTyped,mcliment/DefinitelyTyped,borisyankov/DefinitelyTyped,dsebastien/DefinitelyTyped,georgemarshall/DefinitelyTyped,dsebastien/DefinitelyTyped,georgemarshall/DefinitelyTyped,georgemarshall/DefinitelyTyped