Making Docker image compatible with arm64

[paulosousadias]

Is your feature request related to a problem? Please describe.
Not a specific problem, just needed to deploy on a arm64 architecture.

Describe the solution you would like
Modified the Dockerfile, really a small adjustment in the getting the tiny command

Describe alternatives you have considered
A simple change in the web/docker/Dockerfile make it able to work for amd64 and arm64. See diff bellow

#diff Dockerfile.base Dockerfile
43c43
< FROM python:3.9.7-slim-buster
---
> FROM python:3.9.7-slim-buster as base-stage
133a134,136
> 
> ## For --platform=linux/amd64
> FROM base-stage as stage-amd64
134a138,151
> 
> 
> ## For --platform=linux/arm64
> FROM base-stage as stage-arm64
> ADD https://github.com/krallin/tini/releases/download/${TINI_VERSION}/tini-arm64 /tini
> 
> 
> ## Final stage
> # Declare TARGETARCH to make it available
> ARG TARGETARCH
> # Select final stage based on TARGETARCH ARG
> FROM stage-${TARGETARCH} as final
> 
> 
144a162
> 

Additional context