[FR] GitLab and GitHub integration

### Description

As a project manager I would like to use AppFlowy not only as a knowledge database, but also to manage my projects. For this I create tasks for development teams who use GitLab (public and private) and GitHub for their coding and often for their issue tracking.

- It would be helpful if I could link a page to this GitLab/GitHub issue (maybe via its own property?) and use webhooks to update the information in AppFlowy.
- Additionally if AppFlowy could create an issue in GitLab/GitHub (multiple repositories configured in Workspace) once I create a new issue, it would speed up collaboration with development teams.
- Mirroring comments, status, merge request, and pipelin information from GitLab/GitHub to AppFlowy

### Impact

Projectmanagers and developers in a company using AppFlowy for projects, but tracking code and issues in GitLab/GitHub.

### Additional Context

As an example the integration we currently use in OpenProject: