Update issue templates

.github/ISSUE_TEMPLATE/release-new-version-of-devcontainer.md

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+---
+name: Release new version of devcontainer
+about: Steps to take before release
+title: Release version [number]
+labels: ''
+assignees: ''
+
+---
+
+Checklist for release:
+
+ - [ ] Update NEWS file
+ - [ ] Update CITATION.cff
+ - [ ] Update VERSION
+ - [ ] In devcontainer.json, update `"image": "ghcr.io/r-devel/r-dev-env:devel"` to `"image": "ghcr.io/r-devel/r-dev-env:main"`,,
+ - [ ] Make PR to main branch - needs approving review!
+ - [ ] Make sure docker container is rebuilt
+ - [ ] Test container and fix any issues
+ - [ ] Make GitHub release
+ - [ ] Rebuild docs