threading support controls? seems docs need update

[glycerine]

tinygo-site/content/docs/guides/tips-n-tricks.md

Line 11 in 9d0a8d5

TinyGo code runs on a single core, in a single thread (think `GOMAXPROCS=1`).

says

"TinyGo code runs on a single core, in a single thread (think GOMAXPROCS=1).
Since scheduling in TinyGo is [cooperative]"

However, the latest release notes, under runtime, says

"darwin: add threading support and use it by default"

which seems to contradict the single threaded cooperative concurrency claim of the doc/web site.

Also it would be great to link to what settings are available/ how to control the new concurrency options.

[aykevl]

You are right, see: #461