Added RawContainer support to changelog (flyteorg#375)

Milestone v0.4.0 (flyteorg#331)

Versions:
IDL: [v0.17.32](https://github.com/lyft/flyteidl/releases/tag/v0.17.30)
Admin: [v0.2.8](https://github.com/lyft/flyteadmin/releases/tag/v0.2.8)
Propeller: [v0.2.45](https://github.com/lyft/flytepropeller/releases/tag/v0.2.45)
DataCatalog: [v0.2.1](https://github.com/lyft/datacatalog/releases/tag/v0.2.1)
Flytekit: [v0.8.1](https://github.com/lyft/flytekit/releases/tag/v0.8.1)
FlyteConsole: [v0.5.3](https://github.com/lyft/flyteconsole/releases/tag/v0.5.3)
FlytePlugins: [v0.3.28](https://github.com/lyft/flyteplugins/releases/tag/v0.3.28)

Milestone 0.3.0 release (flyteorg#302)

Tracker branch for Milestone v0.2.0 (flyteorg#230)

Updated the slack link to point to Google form for now (flyteorg#113)