Alpine instead of ubuntu about mattermost-docker

[eungjun-yi]

The reason I am using Ubuntu is because mattermost provides the install guide, which makes it easy to build and maintain the docker image. For example, I just linked the document in my README.md to save my time. :)

I agree with you that smaller is better but I'm not yet sure whether it is important enough.

[enahum]

@npcode that being said then if we write an install guide for alpine you would consider moving the image to use alpine? this is only thinking about smaller containers, nothing else really

[eungjun-yi]

@enahum Sure!

[enahum]

Ok then next steps are:

1. Write an install guide for alpine linux
2. Move docker images to use alpine linux

anything else comes to mind?

[eungjun-yi]

@enahum It seems to be enough. Thanks!

[auguster]

I just had some fun converting the Dockerfile of app to Alpine, the image's size shrunk from 298.5 MB to 90.41 MB. It's really worth it :)

[esethna]

If anyone from the community is interested in writing an install guide for alpine linux, please feel free to submit a PR to the docs repo. Thanks!