Add guide for maintainers to this track.

docs/MAINTAINING.md

+# Welcome!
+
+This is a guide/reference for maintainers of the Java track.
+
+- [Your New Permissions](#your-new-permissions)
+- [Maintainer Guides](#maintainer-guides)
+- [The Project Board](#the-project-board)
+- [Miscellaneous](#miscellaneous)
+
+## Your New Permissions 
+
+You now have write access to four repositories.  "write access" means you can: review, reject, accept and merge PRs; and push changes to these repos.  Despite having permissions to push, we tend to see review of even our own PRs.
+
+- [x-common](https://github.com/exercism/x-common) — the library of exercises.
+- [discussions](https://github.com/exercism/discussions) — the place where project-wide conversations happen. 
+  [issues sorted by most recently updated.](https://github.com/exercism/discussions/issues?q=is%3Aissue+is%3Aopen+sort%3Aupdated-desc)
+- [xjava](https://github.com/exercism/xjava) — yeah... you know what this one is. :)
+- [todo](https://github.com/exercism/todo) — not really used... might just go away completely in the future.
+
+## Maintainer Guides
+
+- **[exercism.io/docs/maintaining-a-track.md](https://github.com/exercism/exercism.io/blob/master/docs/maintaining-a-track.md)**
+- [exercism.io/docs/getting-involved-in-a-track.md](https://github.com/exercism/exercism.io/blob/master/docs/getting-involved-in-a-track.md)
+- [exercism.io/docs/reviewing-a-pull-request.md](https://github.com/exercism/exercism.io/blob/master/docs/reviewing-a-pull-request.md)
+
+## The Project Board
+
+GitHub issues are great, there's no way to easily set priorities.
+To do this, we're using a GitHub Project: https://github.com/exercism/xjava/projects/2.
+
+- **Epics** — issues that really represent bigger ideas.  These inspire creating a set of smaller issues to be elaborated...
+- **Icebox** — issues that just needs a little more detail to be "ready to play"...
+- **Backlog** — issues ready to be worked.  When we start working on an issue, we move it to the next column...
+- **Current** — issues in progress.  When we've considered it done, we move the card to...
+- **Delivered** — completed issues that could use another pair of eyes.  When these are reviewed they get moved to...
+- **Done** — issues we've complete.  Every so often, we get together and it's nice to review what we've completed. 
+  Once reviewed, we remove them from this Project.
+
+The point of this board is to make clear our shared priorities.  It's a tool you can use.
+However, if you have an idea and want to implement it, you can just do it; it does not have to be added to this board.
+
+## Miscellaneous
+
+- Issues marked with "policy" are current "team agreements": [exercism?label:policy](https://github.com/search?q=org%3Aexercism+label%3Apolicy).
+  This label is described in [discussions#96](https://github.com/exercism/discussions/issues/96).
+- Exercism has a Twitter account: [@Exercism.io](https://twitter.com/exercism_io); and a mailing list: https://tinyletter.com/exercism
+
+**Please feel free to ask any questions.  In our thinking, asking questions is far smarter than guessing.**