add v0.1 release branch (knative#821)

* add v0.1 release branch 

and provide some indication that the website is coming

* Update doc-releases.md

Co-Authored-By: RichieEscarez <[email protected]>

* temporarily move the TBD link to the bottom

Fix syntax of Knative install command (knative#736)

Reverting the namespace rename knative-monitoring (knative#486)