Base image size is unnecessarily large

The base container for the azure-vote-app is 922 MB in size. This can be improved significantly, by using an Alpine based image instead of Ubuntu. This is good for at least two reasons:
1: Download/upload times decreases which is very good in e.g. a workshop where several participants share the same WIFI (talking from experience here...)

2: Best practice with containers is to keep them as small as possible

I can make a PR with a smaller image referenced in the Dockerfile, if that would be appreciated

Start by locating the azure-vote-app Dockerfile and reviewing its current base image. Try the proposed Alpine-based image, build the container, and compare its size with the reported 922 MB image. Done means the app still builds and runs while the base image is significantly smaller.

Written by the indexing model from the issue text.