Make it more discoverable and in prep for adding new content.
Also make the use of "Envoy" in top level titles consistent.
We don't need to say "Envoy" in general as all of the documentation
is about Envoy.
Signed-off-by: Matt Klein <mklein@lyft.com>
This should provide an example of how to do the .proto doc linking,
refactoring and constraint addition for the full API.
Signed-off-by: Harvey Tuch <htuch@google.com>
1) Allow release string to be specified by env var
2) Add pre-release warning text
This will be overriden during the official tagged doc builds in the main repo.
Signed-off-by: Matt Klein <mklein@lyft.com>