Add "Edit this page" functionality

[bmorelli25]

Overview

To encourage community contributions and make it easier for users to suggest improvements to our documentation, we should implement an "Edit this page" button on each documentation page. This button would link directly to the corresponding Markdown file on GitHub, allowing users to quickly propose changes.

Acceptance Criteria

• Add an "Edit this page" button to every documentation page
• Button should link to the correct Markdown file in the GitHub repository
• Link should open in GitHub's edit mode (using the /edit/main/ path)
• Links should point to the correct branch (main)
• Functionality should work across all documentation pages

Additional Notes

• Could potentially track usage metrics to see how often this feature leads to contributions

Examples

• elastic/docs
• Vue.js (bottom of page)