Add @types to DefinitelyTyped

[kkmuffme]

Would be great if the types could be added to https://github.com/DefinitelyTyped/DefinitelyTyped

[brendankenny]

web-vitals ships with its own types so doesn't need an entry in Definitely Typed. Are the types not working for you?

[kkmuffme]

They don't work when using the IIFE (e.g. via https://unpkg.com/web-vitals@3.1.1/dist/web-vitals.iife.js) since var webVitals is reported as {}
This is due to the .d.ts being a module (export/import in the .d.ts), therefore only window.webVitals works as expected but using just the webVitals variable reports an error.