Add axe linter as recommended extension for VS Code

What does this MR do and why?

1. Adds axe linter as recommended extension for VS Code
2. Adds custom mapping for Pajamas components
3. Adds documentation about using the linter

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Element	Linting in action
gl-button with text content	Screen Recording 2024-03-01 at 17.29.03.mov
gl-button with icon only	Screen Recording 2024-03-01 at 17.28.10.mov
gl-avatar	Screen Recording 2024-03-01 at 17.26.30.mov
gl-toggle	Screen Recording 2024-03-01 at 17.26.09.mov

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. In VS Code, install axe Accessibility linter plugin
2. Search for components added to yml file and remove accessibility attributes/text content.