Add release checklist.

.bumpversion.cfg

@@ -8,3 +8,5 @@ tag = False
 [bumpversion:file:Cargo.lock]
 
 [bumpversion:file:.github/ISSUE_TEMPLATE/bug_report.yml]
+
+[bumpversion:file:.github/ISSUE_TEMPLATE/release.md]

.github/ISSUE_TEMPLATE/release.md

@@ -0,0 +1,19 @@
+---
+name: Release checklist
+about: '[for maintainer use]'
+title: 'Release 0.3.0'
+labels: ''
+assignees: 'joaander'
+
+---
+
+- [ ] Run *bumpversion*.
+- [ ] Run `cargo update`
+- [ ] Run `cargo bundle-licenses --format yaml --output THIRDPARTY.yaml`
+- [ ] Check for new or duplicate contributors since the last release:
+  `comm -13 (git log $(git describe --tags --abbrev=0) --format="%aN <%aE>" | sort | uniq | psub) (git log --format="%aN <%aE>" | sort | uniq | psub)`.
+  Add entries to `.mailmap` to remove duplicates.
+- [ ] Add release date and highlights to release notes.
+- [ ] Check readthedocs build, especially release notes formatting.
+- [ ] Tag and push.
+- [ ] Update conda-forge recipe.