Small bug and typo fixes

[Msanzdelrio]

This pull request includes changes that refine the documentation and update the development environment configuration. The changes mainly focus on correcting typos, renumbering sections, removing an unnecessary section, and adding a new extension to the development container.

Documentation improvements:

• docs/002-building-a-rest-api.md: Corrected typos and renumbered sections for better understanding. [1] [2] [3] [4] [5]
• docs/002-building-a-rest-api.md: Removed an unnecessary section about adding a new endpoint.
• docs/004-deploying-the-application.md: Added a tip about using Copilot for troubleshooting.

Development environment configuration:

• .devcontainer/devcontainer.json: Added GitHub.copilot-chat to the list of extensions for the development container.

[tgrall]

LGTM