An interesting idea would be one or more BBCodes for GitHub:

• [GitHub]Link[/GitHub] - Examines the Link and post an entity with information regarding the link (for example Issue information or Project Information)
• [issue]#123[/issue] - For a predefined GitHub (maybe also GitLab Project) get the related information for the issue
• [pr]#123[/pr] - For a predefined GitHub (maybe also GitLab Project) get the related information for the pull/merge request