Tag nightlies as prerelease releases (#3892)

This does 2 main things:
- Sets each nightly release as a prerelease on GH's [releases](https://github.com/vercel/turbo/releases) page
- Adds a [notice annotation](https://www.npmjs.com/package/@actions/core#:~:text=These%20will%20surface%20to%20the%20UI%20in%20the%20Actions%20page%20and%20on%20Pull%20Requests.%20They%20look%20something%20like%20this%3A) to the workflow, so that the new tag is logged in the workflow's execution

Additionally, it fixes the `pnpm` workspace so that the action's dist code is actually built. This also means we'll finally see the output of #3819 in our release bodies.

.github/actions/turbopack-bump/package.json

@@ -3,8 +3,8 @@
   "private": true,
   "version": "1.0.0",
   "scripts": {
-    "build:index": "ncc build src/index.ts -o dist --source-map --minify",
-    "prepare": "npm run build:index"
+    "build": "ncc build src/index.ts -o dist --source-map --minify",
+    "prepare": "npm run build"
   },
   "dependencies": {
     "@actions/core": "^1.10.0",

.github/actions/turbopack-bump/src/index.ts

@@ -51,6 +51,7 @@ async function run() {
 
   core.setOutput("new_tag", nextTag);
   await createTag(octokit, nextTag, commitSha);
+  core.notice(`New tag is ${nextTag}`);
 
   // TODO: generate real release notes
   core.setOutput(

.github/workflows/turbopack-nightly-release.yml

@@ -33,3 +33,4 @@ jobs:
           tag: ${{ steps.tag_version.outputs.new_tag }}
           name: Turbopack Nightly Release ${{ steps.tag_version.outputs.new_tag }}
           body: ${{ steps.tag_version.outputs.changelog }}
+          prerelease: true