feat(astro): add support for footer override

[RonithManikonda]

adds support for overriding the footer component, similar to the TopBar override setup. Users can now customize footer content such as legal terms, contact info, and copyrights.

this change introduces Footer.astro and FooterWrapper.astro files to allow flexible slotting of footer items, improving customization for standalone tutorial deployments

close #323

[bolt-new-by-stackblitz[bot]]

Run & review this pull request in StackBlitz Codeflow.

[cloudflare-workers-and-pages[bot]]

Deploying tutorialkit-demo-page with    Cloudflare Pages

Latest commit:	67a5d3e
Status:	✅  Deploy successful!
Preview URL:	https://c80e370a.tutorialkit-demo-page.pages.dev
Branch Preview URL:	https://ronith-overriding-footer.tutorialkit-demo-page.pages.dev

View logs