Add the Check Release workflow

[jtpio]

Problem

The cookiecutter repo should already be compatible with the Jupyter Releaser: https://github.com/jupyter-server/jupyter_releaser

However we should also add the check release workflow so the generated repo can be continuously tested to be release ready.

Proposed Solution

We add a default Check Release workflow to: https://github.com/jupyterlab/extension-cookiecutter-ts/tree/3.0/%7B%7Bcookiecutter.python_name%7D%7D/.github/workflows

Additional context

Here is an example with the jupyterlab-cell-fash extension which has adopted the Jupyter Releaser for automated releases:

https://github.com/jupyterlab-contrib/jupyterlab-cell-flash/blob/main/.github/workflows/check-release.yml