Improve contextual help to mention releases REST API

In tag and releases screen, update contextual help to:

You can manage the project's releases and tags from this screen. Releases can be performed either from a commit in the branch management screen or using a REST API. [Learn more](https://doc.nuxeo.com/studio/how-to-tag-or-release-your-nuxeo-studio-project?utm_source=studio&utm_medium=releases-contextual-help)

In bm screen, update contextual help to:

Manage the project's branches, versions, explore the commit history and perform releases from this screen. Releases can also be performed using a REST API. [Learn more](https://doc.nuxeo.com/studio/how-to-tag-or-release-your-nuxeo-studio-project?utm_source=studio&utm_medium=releases-contextual-help)