[docs] document how root routes coexist with dynamic api routes (#11591)
[docs] document how root routes coexist with dynamic api routes (#11591)

* document how root routes coexist with dynamic api routes

document how root routes coexist with dynamic api routes - related to https://github.com/zeit/next.js/issues/11542

* Update dynamic-api-routes.md

* Update dynamic-api-routes.md

* Run prettier

Co-authored-by: Tim Neutkens <c2906527566e870efadc59ea5d0cd9114389a5d9@me.com>
azukaru/next.js,azukaru/next.js,flybayer/next.js,flybayer/next.js,flybayer/next.js,zeit/next.js,zeit/next.js,azukaru/next.js,azukaru/next.js,JeromeFitz/next.js,JeromeFitz/next.js,JeromeFitz/next.js,JeromeFitz/next.js,flybayer/next.js,zeit/next.js