Add release instructions to repo

RELEASING.md

@@ -0,0 +1,30 @@
+# Release process for the GitHub Dependency Graph Gradle Plugin
+
+## Preparation
+- Push any outstanding changes to branch main.
+- Check that https://github.com/gradle/github-dependency-graph-gradle-plugin/actions is green for all workflows for the main branch.
+- Decide on the version number to use for the release. The plugin releases should follow semantic versioning.
+    - By default, a patch release is assumed (eg. `1.3.0` → `1.3.1`)
+    - If new features have been added, bump the minor version (eg `1.3.1` → `1.4.0`)
+    - If a new major release is required, bump the major version (eg `1.3.1` → `2.0.0`)
+    - Note: The plugin releases follow the semantic version convention of including a .0 patch number for the first release of a minor version, unlike the Gradle convention which omits the trailing .0.
+- Update `release/version.txt` with the to-be-published version
+- Ensure that `release/changes.md` contains all changes that should be included in the release notes
+
+## Run the staging release workflow and verify the published plugin
+- Publish to staging by executing the [staging release workflow](https://github.com/gradle/dv-solutions/actions/workflows/github-dependency-graph-gradle-plugin-staging-release.yml) job.
+  - Run the workflow from the `main` branch and enter "STAGING" when requested.
+  - Once the workflow is complete, check that it was published successfully at https://plugins.grdev.net/plugin/org.gradle.github-dependency-graph-gradle-plugin
+- If necessary, run a build that resolves and tests the newly published plugin
+
+## Run the production release workflow and verify the published plugin
+- Publish to production by executing the [production release workflow](https://github.com/gradle/dv-solutions/actions/workflows/github-dependency-graph-gradle-plugin-production-release.yml) job.
+    - Run the workflow from the `main` branch and enter "PRODUCTION" when requested.
+- After the workflow completes, check the outputs:
+    - Verify that the plugin is available at https://plugins.gradle.org/plugin/org.gradle.github-dependency-graph-gradle-plugin
+    - If necessary, run a build that resolves and tests the newly published plugin
+    - Check that the GitHub release was generated at https://github.com/gradle/github-dependency-graph-gradle-plugin/releases
+
+## Update `gradle/actions` to use the newly published release
+- Update the default value for `dependency-graph-plugin.version` [here](https://github.com/gradle/actions/blob/main/sources/src/resources/init-scripts/gradle-actions.github-dependency-graph-gradle-plugin-apply.groovy#L9), to reference the new release.
+  - Submit a PR with this change.