Add milestones field in the projects frontmatter and display it in the project description.

Currently, all the GSoC projects contain a lot of issues being displayed. IMO, it would be better to just add the Gitlab milestones instead of all the issues because some issues may be closed or more issues may be created over the time.

Start by locating the project frontmatter definition and the renderer for project descriptions. Trace how GitLab issues are currently collected and displayed, then identify where milestones should be read and shown instead. Done means a project can declare milestones in frontmatter and its description displays those milestones rather than the full issue list.

Written by the indexing model from the issue text.