build: specify a high network timeout in root .yarnc
build: specify a high network timeout in root .yarnc

Yarn can be sensitive to timeouts when downloading large-ish packages that
aren't in its cache, e.g. `@reactivex/rxjs`. Specify a high-timeout in the root
`.yarnrc` to workaround `yarn install` hanging indefinitely and reporting
network connection errors, which seems to be experienced more frequently on
Windows than on Linux or macOS. Note: this is probably buggy behavior on yarn's
part.

iurimatias/embark-framework,iurimatias/embark-framework