Push images on very main commit

[JaveriaK]

Our environment uses a UDP statsd collector. In ref to: #157 , since the actual changeset that supported a UDP sink (lyft/gostats#95) was merged after envoyproxy/ratelimit:v1.4.0 was cut; can we please get a newer tag upstream for the ratelimit image?
This can done with a local build but we'd prefer pulling an official upstream tagged image.

[mattklein123]

I would really like to get out of the business of having to explicitly tag releases.

@stevesloka can we potentially push images on every main commit tagged by SHA? I think that would be a lot easier given the relatively small number of commits we have on this project.

[stevesloka]

@mattklein123 yup we can do that! I'm happy to put a PR together to do that.

[mattklein123]

Thank you!