feat: Add Astro Framework Support

## Summary

This issue tracks the addition of official **Astro framework** support to the SocialShareButton library.

## Background

PR #33 (https://github.com/AOSSIE-Org/SocialShareButton/pull/33) introduced documentation updates for Astro support in the Quick Start Guide. This issue tracks the full implementation and integration of Astro framework support.

## Tasks

- [ ] Implement Astro-compatible component or integration for SocialShareButton
- [ ] Add Astro-specific usage examples and documentation
- [ ] Handle server-side rendering (SSR) behavior specific to Astro
- [ ] Update the Quick Start Guide with Astro installation and usage instructions
- [ ] Test the integration with Astro projects

## References

- PR: https://github.com/AOSSIE-Org/SocialShareButton/pull/33
- Requested by: @kpj2006
- To be worked on by: @edengilbertus