docs: [#315] Add backup container workflow badge to README

Added [![Backup Container](...)](/actions/workflows/backup-container.yaml)
badge alongside other workflow status indicators in the main README.

This provides visibility into the backup container build and publish status.

Author: josecelano

README.md

@@ -1,4 +1,4 @@
-[![Linting](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/linting.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/linting.yml) [![Testing](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/testing.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/testing.yml) [![E2E Infrastructure Tests](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/test-e2e-infrastructure.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/test-e2e-infrastructure.yml) [![E2E Deployment Tests](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/test-e2e-deployment.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/test-e2e-deployment.yml) [![Test LXD Container Provisioning](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/test-lxd-provision.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/test-lxd-provision.yml) [![Coverage](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/coverage.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/coverage.yml) [![Container](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/container.yaml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/container.yaml) [![Docker Security Scan](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/docker-security-scan.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/docker-security-scan.yml)
+[![Linting](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/linting.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/linting.yml) [![Testing](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/testing.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/testing.yml) [![E2E Infrastructure Tests](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/test-e2e-infrastructure.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/test-e2e-infrastructure.yml) [![E2E Deployment Tests](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/test-e2e-deployment.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/test-e2e-deployment.yml) [![Test LXD Container Provisioning](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/test-lxd-provision.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/test-lxd-provision.yml) [![Coverage](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/coverage.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/coverage.yml) [![Container](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/container.yaml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/container.yaml) [![Backup Container](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/backup-container.yaml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/backup-container.yaml) [![Docker Security Scan](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/docker-security-scan.yml/badge.svg)](https://github.com/torrust/torrust-tracker-deployer/actions/workflows/docker-security-scan.yml)
 
 # Torrust Tracker Deployer