[Meta] Release Prep and Announcement

[Mikaayenson]

Summary

Here's a list of items we should prepare before releasing:

Tasks

• Adding a CONTRIBUTING guide.
• Adding the repo to catalog info - https://github.com/elastic/catalog-info/pull/1609
• Adding issue templates
• Adding a pull request template
• Adding a CODEOWNERS, LICENSE.txt, NOTICE.txt file -- chore: Adding necessary pieces for Cortado repo #18
• Adding a community GitHub action workflow - chore: Adding necessary pieces for Cortado repo #18
• Updating the readme with questions and a reference to the license, pointing people to community slack channel if needed
• Follow up with https://github.com/elastic/open-source guidance
• chore(ci): new CI action trigger for REACT testing workflow detection-rules#4435
• https://github.com/elastic/react/pull/250
• feat: Syncing latest RTAs delta from detection-rules repo #19
• https://github.com/elastic/open-source/issues/463
• Remove RTAs from detection-rules repo, provide reference to Cortado, and tag, then release announcement blog with the version chore: Removing RTAs detection-rules#4437

cc. @elastic/open-source-wg