Add a custom template for the release note text pushed to github

Hi
following instructions in https://github-tools.github.io/github-release-notes/options.html
I tried to customize the header text in order to have a default text in the github release note using the "release" template.
However it seems to act only on the changelog.md and not on the release note on github.

Start with the documented "release" template option and trace how its header text is applied to changelog.md versus the GitHub release note. Compare both generated outputs and verify that the configured default text appears in the GitHub release body as well as the changelog.

Escrito por el modelo de indexación a partir del texto del issue.