provide example mmf as docker image on gcr

[dzmitry-lahoda]

Is your feature request related to a problem? Please describe. it is hard to write mmf without go and grasp workings of it from scratch

Describe the solution you'd like

• build mmf backfil examples and publish as docker
• count of player per match to be defined as ENV var
• merge profile extensions and pool string fields as extensions of generated match (so that GA can use it for allocation)

Describe alternatives you've considered I am modified MMF backfill and published to local docker. I did not modified logic, only passing metadata and env vars around.

Additional context Some set of MMFs with well defined behaviours could be usefull as docker examples on gcr