docs: add RELEASING instructions

RELEASING.md

@@ -0,0 +1,40 @@
+# Releasing
+
+This describes how to release `dagger-for-github`.
+
+The action's `README.md` and `action.yml` should be relatively evergreen now,
+so we don't need to bump with Dagger releases anymore, just if there is a fix
+to `dagger-for-github`. We'll use `8.0.0` style versions for the action going
+forward to comply with GitHub immutable actions standards. Should not need
+separate `v8` tag. Should automatically get `v8`, `v8.0`, `v8.0.0` as well as
+`8.0.0` resolved by GitHub.
+
+## Let the team know
+
+- [ ] When preparing a release (as mentioned in `dagger/dagger`'s
+      [`RELEASING.md`](https://github.com/dagger/dagger/blob/main/RELEASING.md),
+      include whether there should be a new `dagger-for-github` release as well.
+
+- [ ] Take a peek at the action or mention it in the release thread on Discord
+      to determine if there are updates to reflect in the docs.
+
+- [ ] Create/push a new patch tag for fixes/changes to `dagger-for-github`
+
+```console
+# Find the latest released patch https://github.com/dagger/dagger-for-github/releases
+# or via the `gh` CLI. Use that to figure out the NEXT_PATCH_VERSION.
+gh release view --repo dagger/dagger-for-github --json tagName,publishedAt
+
+# Sign the tag, using the date as the comment, e.g. 2024-07-22
+git tag --sign -m $(date '+%Y-%m-%d') <NEXT_PATCH_VERSION>
+git push origin <NEXT_PATCH_VERSION> #shouldn't need to force since new tag
+```
+
+- [ ] Create a new release from the patch tag (auto-fill release notes via the
+      GitHub UI or via the `gh` CLI)
+- [ ] Submit PR to change the version mentioned in Dagger docs. See example [here](https://github.com/dagger/dagger/pull/9705/files)
+
+```console
+# --verify-tag will ensure the last tag creation step was done
+gh release create --generate-notes --verify-tag <NEXT_PATCH_VERSION>
+```