chore: Move from yarn to npm

Spoke with @rjbeers about this. yarn 1.22 is very old and newer version of yarn aren't really used in frontend projects. Typically npm or pnpm is used these days. Let's move to standard npm. So we'll remove the yarn.lock file and commit the package-lock.json once `npm install` is run. Also, we should add yarn.lock to the .gitignore