* Add sd-streams from https://github.com/stardazed/sd-streams/blob/master/packages/streams/src/

* change the interfaces in dom_types to match what sd-streams expects

Worth noting due to implementation of the Headers class the contents of headersMap have lowercase keys, although this matches the specification as header keys are case agnostic it does seem to not match behaviour of other implementations in other languages I have seen, would require some rewriting of Headers.ts

Fixes #3163
Co-authored-by: NKitson Kelly <me@kitsonkelly.com>
Co-authored-by: NQwerasd <qwerasd205@users.noreply.github.com>

We changed our markdown parser from showdown to remark for better react
integration, and it necessitated this change.

Move manual.md and style_guide.md into //std so they can be accessed
from https://deno.land/std/manual.md

Code for new website is https://github.com/denoland/deno_website2Co-authored-by: NChristian Moritz <chrmoritz@gmail.com>

https://github.blog/changelog/2019-10-17-github-actions-default-shell-on-windows-runners-is-changing-to-powershell/