Add a release guide

Signed-off-by: Håkon Wiik Ånes <hwaanes@gmail.com>

RELEASE.rst

@@ -0,0 +1,53 @@
+How to make a new release of ``kikuchipy``
+==========================================
+
+This guide should be updated after every new release!
+
+- Create a release branch v<major>.<minor>.x. If a new minor release is to be
+  made, branch off of master via the GitHub repo, and pull this branch locally.
+  If a new patch release is to be made, pull the existing minor branch locally
+  and branch off of it.
+
+- Review and clean up doc/changelog.rst as per Keep a Changelog. Make sure all
+  contributors and reviewers are acknowledged. Increment the version number in
+  `release.py`. Make a PR to the release branch.
+
+- Create a PR from the release branch to master. Discuss the changelog with
+  others, and make the changes directly to the release branch. After all checks
+  are green and the PR is merged, cherry-pick any resulting changes to the
+  release branch.
+
+- Make sure that the documentation, with the changelog updates, can be
+  successfully built from the release branch by making Read the Docs build the
+  release branch: https://readthedocs.org/projects/kikuchipy/.
+
+- On the master branch, increment the version number in `release.py` to the next
+  ``.dev0``.
+
+- Create a release draft (tag) via the GitHub repo from the release branch with
+  the correct tag version name, e.g. v0.42.x and release title (see previous
+  releases). Add the new release notes from the changelog. Publish the release.
+
+- Monitor Travis CI to ensure the release is successfully published to PyPI.
+
+conda-forge
+-----------
+
+A kikuchipy build recipe is available at
+https://github.com/conda-forge/kikuchipy-feedstock. conda-forge documentation is
+available at https://conda-forge.org/docs/index.html.
+
+- Fork the feedstock.
+
+- Create a new release branch named v<major>.<minor>.x off of master.
+
+- Increment the version number in `recipe/meta.yml`. Get the SHA256 for the
+  package distribution (`.tar.gz`) from PyPI
+  https://pypi.org/project/kikuchipy/.
+
+- Make a PR to master from the release branch. Follow the relevant instructions
+  from the conda-forge documentation on updating packages. Merge the PR after
+  all checks are green.
+
+- Monitor the Azure pipeline CI to ensure the release is successfully published
+  to conda-forge.