Milestones for release plan

[kangz12345]

I would like to suggest we use milestones for release plans.

For example:

1. Decide which features should be included in the next release.
2. Based on the included features, decide the name of the next release (e.g. 0.1.2-alpha).
3. Decide the due date of the release.
4. Create a milestone with the release name and the due date.
5. Add it to the issues for the included features.