adds release.md (#86)

* adds release.md

* review

* Update RELEASE.md

Co-authored-by: Jeremy Tuloup <jeremy.tuloup@gmail.com>

Author: hbcarlos

RELEASE.md

@@ -0,0 +1,72 @@
+# Making a new release of JupyterLab-DrawIO
+
+## Getting a clean environment
+
+Creating a new environment can help avoid pushing local changes and any extra tag.
+
+```bash
+mamba create -q -y -n drawio-release -c conda-forge twine nodejs keyring pip matplotlib jupyter-packaging jupyterlab
+conda activate drawio-release
+```
+
+Alternatively, the local repository can be cleaned with:
+
+```bash
+git clean -fdx
+```
+
+## Releasing on PyPI
+
+Make sure the `dist/` folder is empty.
+
+1. Update [package.json](./package.json) and [binder/environment.yml](./binder/environment.yml) with the new version number
+2. `python setup.py sdist bdist_wheel`
+3. Double check the size of the bundles in the `dist/` folder
+4. Run the tests
+5. Make sure the JupyterLab extension is correctly bundled in source distribution
+6. `export TWINE_USERNAME=mypypi_username`
+7. `twine upload dist/*`
+
+# Making a new release of jupyterlab-drawio
+
+The prebuilt extension is already packaged in the main Python package.
+
+However we also publish it to `npm` to:
+
+- let other third-party extensions depend on `jupyterlab-drawio`
+- let users install from source if they would like to
+- bundle the extension into the JupyterLab app
+
+## Releasing on npm
+
+1. The version number in [package.json](./package.json) should have been updated during the release step of the Python package (see above)
+2. `npm login`
+3. `npm publish`
+
+## Releasing on conda-forge
+
+> The next steps aren't valid for now. We don't have a recipe for jupyterlab-drawio yet.
+
+The simplest is to wait for the bot to automatically open the PR.
+
+Alternatively, to do the update manually:
+
+1. Open a new PR on https://github.com/conda-forge/jupyterlab-drawio-feedstock to update the `version` and the `sha256` hash (see [example](https://github.com/conda-forge/jupyterlab-drawio-feedstock/pull/12/files))
+2. Wait for the tests
+3. Merge the PR
+
+The new version will be available on `conda-forge` soon after.
+
+## Committing and tagging
+
+Commit the changes, create a new release tag, and update the `stable` branch (for Binder), where `x.y.z` denotes the new version:
+
+```bash
+git checkout master
+git add binder/environment.yml package.json
+git commit -m "Release x.y.z"
+git tag x.y.z
+git checkout stable
+git reset --hard master
+git push origin master stable x.y.z
+```