TypeScript Definitely Typed
Sometimes the projects are no longer maintained, and other times they aren't interested in, agree with, or have time to use TypeScript.
Using non-typed NPM packages in TypeScript
Using untyped NPM packages with TypeScript will not be type safe due to lack of types.
To help TypeScript developers use such packages, there is a community maintained project called Definitely Typed.
Definitely Typed is a project that provides a central repository of TypeScript definitions for NPM packages which do not have types.
No other steps are usually needed to use the types after installing the declaration package, TypeScript will automatically pick up the types when using the package itself.
Editors such as Visual Studio Code will often suggest installing packages like these when types are missing.