When I try to import ReactDiffViewer, typescript throws this nasty error: "Could not find a declaration file for module...implicitly has an 'any' type." Turns out, the solution is simple, which you can find here: https://stackoverflow.com/questions/41292559/could-not-find-a-declaration-file-for-module-module-name-path-to-module-nam.
Tl;dr: could you please modify your package.json to have these two lines?
"main": "lib/index",
"typings": "lib/index",
^ removes the .js at the end of "lib/index.js" and adds typings
This solved the problem locally for me, but it'd be nice if this fix was automatically included for everyone!