Bump to version 20.12.1

Bump to v20.12 (sanic-org#1987)

* Bump to v20.12

* Update Changelog

Prepare for release

Ignore writing headers when in ASGI mode (sanic-org#1957)

* Ignore writing headers when in ASGI mode for streaming responses

* Move asgi set on streaming until after response type check

* Adds multidict==5.0.0 to pass tests

* Bump version to 20.9.1

Merge branch '19.12LTS' of github.com:huge-success/sanic into 19.12LTS

Version 20.9 (sanic-org#1940)

V2.6.3 changelog (sanic-org#1886)

* Version

* Version 20.6.1

* v2.6.3 changelog and version

Merge branch 'master' of github.com:huge-success/sanic

v2.6.3 changelog and version

Merge branch 'master' of github.com:huge-success/sanic