Add Feature/asynq worker

[noxymon-mekari]

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

Problem/Feature

This pull request introduces a new "Worker" feature to the project, allowing users to add background worker functionality using Asynq with Redis. The changes include updates to the feature flag system, the project creation process, and the addition of extensive tests for the new functionality.

Description of Changes:

• Added a new Worker constant and included it in the AllowedAdvancedFeatures list in cmd/flags/advancedFeatures.go.
• Updated the project creation logic to handle the "Worker" feature, including generating worker-related files (main.go, hello_world_task.go) and directories (cmd/worker, cmd/worker/tasks) in cmd/program/program.go.
• Modified the environment file generation to include worker-specific environment variables when the "Worker" feature is enabled.
• Added a new option for the "Worker" feature in the advanced step configuration in cmd/steps/steps.go.

Checklist

• I have self-reviewed the changes being requested
• I have updated the documentation (check issue ticket 📋Update documentation if the PR introduces a new feature!📋 #218)