create a release issue template

.gitlab/issue_templates/release.md

+# Release %vX.Y.Z **UPDATE THIS**
+
+This is a checklist based on the [release document](RELEASE.rst); consult it for more details.
+
+## Preflight checks
+
+- [ ] All the issues from this milestone are resolved
+- [ ] Ensure that tests pass (either on [stable](https://gitlab.kwant-project.org/kwant/kwant/tree/stable) or on [master](https://gitlab.kwant-project.org/kwant/kwant/tree/master) branch)
+- [ ] Documentation looks correct https://test.kwant-project.org/doc/<branch name>
+- [ ] [Whatnew](doc/source/pre/whatsnew) is up to date
+- [ ] `AUTHORS.rst` and `.mailmap` are up to date (run `git shortlog -s | sed -e "s/^ *[0-9\t ]*//"| xargs -i sh -c 'grep -q "{}" AUTHORS.rst || echo "{}"'`)
+
+## Make a release, but do not publish it yet
+
+- [ ] Tag the release
+- [ ] Build the source tarball and inspect it
+- [ ] Build the documentation
+
+## Test packaging
+
+These steps may be done in parallel
+
+### Debian
+
+- [ ] Follow the steps for building the Debian packages from [RELEASE.rst](RELEASE.rst)
+
+### Conda
+
+- [ ] Publish the release candidate source tarball "somewhere on the internet" (SOTI)
+- [ ] open a PR to the [conda-forge/kwant-feedstock](https://github.com/conda-forge/kwant-feedstock/) repo on Github. Make sure to mark the PR as WIP so that it doesn't get merged in accidentally
+    - [ ] set the upstream tarball URL (in meta.yaml) to SOTI
+    - [ ] update the tarball hash in meta.yaml
+- [ ] See if the package builds
+
+## Publish the release
+- [ ] push the tag
+- [ ] upload the source tarball to PyPI
+- [ ] upload the source tarball to the Kwant website
+- [ ] publish the debian packages
+- [ ] publish the ubuntu packages
+- [ ] create a new version of the Kwant conda-forge feedstock, and open a pull request to upstream
+- [ ] upload the documentation to the Kwant website
+- [ ] update the Kwant website to say that Conda is the preferred way to install Kwant on Windows
+
+## Announce the release
+- [ ] Write a short post summarizing the highlights on the Kwant website
+- [ ] post to the Kwant mailing list
+
+## Working towards next release
+- [ ] add a whatsnew file for the next release
+- [ ] tag this release with an `a0` suffix
+- [ ] push this tag to the official Kwant repository
+- [ ] create a milestone for the next release

RELEASE.rst

@@ -3,6 +3,10 @@ Making a Kwant release
 
 This document guides a contributor through creating a release of Kwant.
 
+Create a release issue
+######################
+
+Use the correct `issue template <gitlab.kwant-project.org/kwant/kwant/issues/new?issuable_template=release>`_, adjust it if necessary.
 
 Preflight checks
 ################