Build updates for Grails 7

[jdaugherty]

• Publishes documentation for snapshots
• Updates for grailsPublish
• Fixes links in documentation that were broken
• Adds Emojis for task names @matrei
• Updates release & gradle workflows with new variable names
• Removes older version of groovy and updates for latest grails 7 updates (i.e. toolchain replacement)
• Updates readme.md to README.md to match github style

[jdaugherty]

@codeconsole & @sbglasius I don't have access to the GPC, but this is based on similar work done across grails & grails-plugins repos. Some other examples are https://github.com/grails-plugins/grails-spring-security-ldap, grails-audit-logging, spring-security-rest, etc. Can you two please review this?

[jdaugherty]

I believe grails-build will need access to this repo if it doesn't already have it to auto-increment the version #

[jamesfredley]

ticket created in base-camp to access the invite sent to grails-build

[jamesfredley]

grails-build invite was accepted