[FR] Link to Github

**1~3 main use cases of the proposed feature**
Possibility to connect projects to github organization/repository and connect a property (unique id) in commits or PR to that card

**what types of users can benefit from using your proposed feature**
This can be useful for people that want to use Appflowy as and free, localhosted, simpler alternative to for example Jira

**Additional context**
I'm not sure how this is done with Jira and how dificult it would be to add something like this.