Please check if the PR fulfills these requirements
[x] The commit message follows our guidelines
What kind of change does this PR introduce?
Documentation update
What is the current behavior?
Some pieces of information about the release train course are missing.
What is the new behavior (if this is a feature change)?
Information is added regarding the release notes, migration guides and communication after the release train.
Does this PR introduce a breaking change or deprecate an API?
Please check if the PR fulfills these requirements
What kind of change does this PR introduce? Documentation update
What is the current behavior? Some pieces of information about the release train course are missing.
What is the new behavior (if this is a feature change)? Information is added regarding the release notes, migration guides and communication after the release train.
Does this PR introduce a breaking change or deprecate an API?