Improve prefetch docs (#7692)
Improve prefetch docs (#7692)

* added docs for disabling prefetch

* Update packages/next/README.md

Co-Authored-By: JJ Kasper <7323a5431d1c31072983a6a5bf23745b655ddf59@jjsweb.site>

flybayer/next.js,flybayer/next.js,BlancheXu/test,zeit/next.js,azukaru/next.js,zeit/next.js,azukaru/next.js,BlancheXu/test,azukaru/next.js,azukaru/next.js,flybayer/next.js,BlancheXu/test,JeromeFitz/next.js,zeit/next.js,flybayer/next.js,JeromeFitz/next.js,JeromeFitz/next.js,JeromeFitz/next.js