add v0.1 release branch (#821)

* add v0.1 release branch 

and provide some indication that the website is coming

* Update doc-releases.md

Co-Authored-By: RichieEscarez <rescarez@google.com>

* temporarily move the TBD link to the bottom

doc-releases.md

@@ -3,10 +3,17 @@
 The following list shows the available versions of Knative documentation.
 Select the version that matches your installed version of Knative.
 
-## Released versions
+## `knative/docs` repositories
+
+### Released versions
 
 * [Branch: **`release-0.2`**](https://github.com/knative/docs/tree/release-0.2)
+* [Branch: **`release-0.1`**](https://github.com/knative/docs/tree/release-0.1)
 
-## In development (pre-release) version
+### In development (pre-release) version
 
 * [Branch: **`master`**](https://github.com/knative/docs/tree/master)
+
+## Documentation website
+
+* `https://knative.dev` ([Coming soon!](https://github.com/knative/docs/projects/5))