Include a Latest Binder link for new issues

[ianhi]

Problem

Creating a test environment (https://jupyterlab.readthedocs.io/en/latest/getting_started/issue.html) when reporting an issue can be a bit of a barrier to entry. You can avoid doing this, but then I always feel slightly guilty.

Proposed Solution

Make a binder that creates either the environment specified in the docs for a new issue or creates one based on this repos HEAD.

Add that binder link to both the docs on opening an issue and to the bug-report template.

I thought about using the binder link in the readme, but that doesn't point to the latest jlab as it is pinned to a specific commit in jupyterlab-demo repo.