Auto-trigger the build of the `dev` docker container

MERGE REQUEST

MR Guidelines

Overview

We want to trigger the build of the dev docker container on each successful push to master. This MR adds a "deploy" stage to the CI in which we'll make a POST request to the respective hook.

Example for Visual Changes

Example pipeline triggering a build: https://gitlab.com/NebulousLabs/Sia/-/pipelines/185764459

Here's the moment the pipeline triggers the build:

And here is the build on hub.docker.com (1PM CET is 11AM UTC):

Checklist

Review and complete the checklist to ensure that the MR is complete before assigned to an approver.

• All new methods or updated methods have clear docstrings
• Testing added or updated for new methods
• Any new packages are added to Makefile and .gitlab-ci.yml
• API documentation updated for API updates
• Module README.md updated for changes to workflow
• Issue added to Sia-UI repo for new supporting features
• Changelog File Created

Issues Closed