add AI agent guidance into project-base and shorten monorepo AGENTS.md (#4700)

Author: vitek-rostislav

README.md

@@ -7,7 +7,7 @@ Shopsys Coding Standards are based on [PSR-2](http://www.php-fig.org/psr/psr-2/)
 This project bundles tools along with predefined rulesets for automated checks of Shopsys Coding Standards that we use in many Shopsys projects.
 The repository also contains [few custom rules](#custom-rules).
 
-This repository is maintained by [shopsys/shopsys] monorepo, information about changes is in its `CHANGELOG` file.
+This repository is maintained by [shopsys/shopsys] monorepo. See the [releases](https://github.com/shopsys/shopsys/releases) page for the history of changes.
 
 Provided tools:
 
@@ -88,7 +88,7 @@ Please check our [Contribution Guide](https://github.com/shopsys/shopsys/blob/HE
 ## Support
 
 What to do when you are in troubles or need some help?
-The best way is to join our [Slack](https://join.slack.com/t/shopsysframework/shared_invite/zt-11wx9au4g-e5pXei73UJydHRQ7nVApAQ).
+The best way is to ask in our [GitHub Discussions](https://github.com/shopsys/shopsys/discussions).
 
 If you want to [report issues](https://github.com/shopsys/shopsys/issues/new), please use the main [Shopsys repository](https://github.com/shopsys/shopsys).