message: docs: misc contributing guide updates
diff: @@ -32,6 +32,8 @@ maximize the chances of your PR being merged.
  deprecation window. We make no guarantees about code or deployments that rely on undocumented
  behavior.
  * All deprecations/breaking changes will be clearly listed in [DEPRECATED.md](DEPRECATED.md).
  +* All deprecations/breaking changes will be announced to the
  + [envoy-announce](https://groups.google.com/forum/#!forum/envoy-announce) email list.
  # Release cadence
  @@ -74,6 +76,12 @@ maximize the chances of your PR being merged.
  Closing stale PRs helps us keep on top of all of the work currently in flight.
  * If a commit deprecates a feature, the commit message must mention what has been deprecated.
  Additionally, [DEPRECATED.md](DEPRECATED.md) must be updated as part of the commit.
  +* Please consider joining the [envoy-dev](https://groups.google.com/forum/#!forum/envoy-dev)
  + mailing list.
  +* If your PR involves any changes to
  + [envoy-filter-example](https://github.com/lyft/envoy-filter-example) (for example making a new
  + branch so that CI can pass) it is your responsibility to follow through with merging those
  + changes back to master once the CI dance is done.
  # PR review policy for committers
  @@ -98,6 +106,8 @@ maximize the chances of your PR being merged.
  * Please **clean up the commit message** before merging. By default, GitHub fills the squash merge
  commit message with every individual commit from the PR. Generally, we want a commit message
  that is roughly equal to the original PR title and description.
  +* If a PR includes a deprecation/breaking change, notification should be sent to the
  + [envoy-announce](https://groups.google.com/forum/#!forum/envoy-announce) email list.
  # CLA
  