feat: custom dir on fs storage

[prakasa-tkpd]

Background

Currently for fs storage type will always store profiling result to os.tmpdir(). That is might be hard for beginner developers to find where is the tmpdir in the OS. And refer to the document, we have storage.dir as target custom directory, but currently this option only support for s3. So I think we need to adding storage.dir option to support for fs storage type.

e.g:

const Inspector = require("inspector-api");

const inspector = new Inspector({
   storage: {
     type: "fs",
     dir: "./profile-results",
   },
});

[vincentvalletvoodoo]

Thanks for the work done.
Could you just add a test to validate this use case?