new github action build-push-action for docker development

[dariuschira]

What does it fix?

Closes #270

I added a build and publish workflow that triggers on pushes to master or develop. These will occur when pushing directly or when merging a pull request. Note that it won't occur if a pr is only created.
It will always push with the 'latest' tag

You will need to setup the following credentials as github secrets (similar to the example given):
ORGANIZATION - dockerhub organization
REPO - dockerhub image repository from the above organization (not sure if a new one needs to be created?)
USERNAME and PASSWORD for a user with access to these

You can find more information about the github action here: https://github.com/docker/build-push-action

How has it been tested?

I used a private github repo for testing the secrets setup along side a private dockerhub repository.

There's an issue I encountered, however. This fails though I'm not sure why yet.. I'm not familiar with dotnet but I believe it may be due to invalid credentials setup?

RUN dotnet publish -c Release -o ./out

Results in this during the publish step, when building the image:

... executor failed running [/bin/sh -c dotnet publish -c Release -o ./out]: exit code: 1

Because of (or without the files generated from) the previous error, the following occurs on this step:

COPY --from=build-env /app/api/VoteMonitor.Api/out/ .

Results in this during the publish step, when building the image:

... failed to compute cache key: "/app/api/VoteMonitor.Api/out" not found: not found

[RaduCStefanescu]

Hey @mirceachira
This one looks nice but what happens when you push to develop or master? The image will be built but based on two distinct code bases.
Can you please tag the image accordingly?
dev for develop branch, prod for master branch.

Thanks!