Add type definition for random-useragent package

[jeffryang24]

Dear, Author/Maintainer of random-useragent package.

I just submitted a PR to DefinitelyTyped for this package's type definition. I use your package in my project and I found that there is no type definition yet for this package, so I created the ambient module first, then I create PR for the type.

Please feel free to review my PR at DefinitelyTyped/DefinitelyTyped#35493 in case there is a wrong definition or other problems. Thank you. 🙇‍♂️

[jeffryang24]

Currently, the definition file has been published at https://www.npmjs.com/package/@types/random-useragent 🎉

[skratchdot]

Thank you!