Service: Find similar npm packages

Input: Some package
Output: Packages providing similar functionality

## Problem

Hard to create a similarity score. A lot of parameters:

- keywords / description in `package.json`
- README content
- common dependencies
- common appearance on awesome lists

## Nice-to-have features

- Download stats per package
- GitHub stars
- Display the advantages/disadvantages of the different packages (read something like a `TRADEOFFS.md` or somehow user-contributed)
- Show how well maintained a package is (last publishing, avg time between `user opens issue|PR` and `first reaction`)