* Replaced "Grafana 8 alerting" with "Grafana alerting". Added support matrix for Grafana alerting.
* Few more changes and added deprecation notice to legacy alerting landing page.
* Added more content from Yuri's PR.
* Ran prettier.
* Added code review changes.
* One more change.
* Fixed linked texts.
(cherry picked from commit ae655f2675)
Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>