workflows: instructions for release process

[amtep]

What, How & Why?

Describes the new release process that uses Github Actions.

Please let me know if any step is still unclear.

☑️ ToDos

• [ ] 📝 Changelog entry
• [ ] 📝 Compatibility label is updated or copied from previous entry
• [ ] 🚦 Tests
• [ ] 🔀 Executed flexible sync tests locally if modifying flexible sync
• [ ] 📦 Updated internal package version in consuming package.jsons (if updating internal packages)
• [ ] 📱 Check the React Native/other sample apps work if necessary
• [ ] 📝 Public documentation PR created or is not necessary
• [ ] 💥 Breaking label has been applied or is not necessary

[amtep]

Since we now have prereleases with github actions, I removed the old instructions completely.

I also updated the instructions for the new input fields in prepare release.