docs: add instructions for releasing a new version

docs/astro.config.mjs

@@ -146,6 +146,16 @@ export default defineConfig({
           label: 'Known issues',
           link: '/known-issues',
         },
+        {
+          label: 'Project internals',
+          collapsed: true,
+          items: [
+            {
+              label: 'Releasing a new version',
+              link: '/internal/releasing',
+            }
+          ]
+        },
       ],
     }),
     tailwind({

docs/src/content/docs/internal/releasing.md

@@ -0,0 +1,24 @@
+---
+title: "Releasing a new version"
+---
+
+Releasing a new version of Tanka requires a couple of manual and automated steps.
+This guide will give you a runbook on how to do them in the right order.
+
+## 1. Create a release tag
+
+1. Pull the latest changes from the `main` branch to your local clone.
+1. Create a new tag with the prefix `v` (e.g. `v0.28.0`).
+1. Push that tag back to GitHub.
+
+This starts multiple GitHub workflows that will produce binaries, a Docker image, and also a new GitHub release that is *marked as draft*.
+
+## 2. Add changelog to the release notes
+
+Once all these actions have finished, go to <https://github.com/grafana/tanka/releases> and you should see the new draft release.
+Click the pencil icon ("edit") at the top-right and go to the last line of the text body.
+Now hit the "Generate release notes" button to add a changelog to the end of the release notes.
+
+## 3. Publish the release notes
+
+Once you've check that the release looks fine (e.g. no broken links, no missing version numbers in the download paths) click the "Publish release" button.