You can share the project by adding collaborators. Here, you can search and add a new collaborator by their GitHub ID. A collaborator can have either Admin or User access rights. A collaborator with admin access rights will have full access (to the settings, as well). A collaborator with user access rights, on the other hand, will have restricted access rights. They will be able to see all builds, but they will not be able to access the backups, logs, shells, or emails of the production or staging branches, though they will have full access for the development branches:
You will need to give access to the GitHub repository to these users, too; otherwise, they won't be able to create a new repository from the browser.