add "next" branch for prereleases

It is strongly recommended to do prerelease before releasing a stable
release because we cannot cancel publishing a package n npm.js; once
a package is uploaded, its version number is occupied forever even if
it is unpublished.  Making a stable version number unavailable due to
failure of uploading or packaging is quite unsatisfactory.  Prerelease
allows us to make sure that a package can be successfully created and
uploaded before stable release.

.github/workflows/ci.yaml

@@ -32,7 +32,7 @@ jobs:
       - run: pnpm --recursive --sequential run build
   release:
     needs: check
-    if: github.ref == 'refs/heads/latest'
+    if: github.ref == 'refs/heads/latest' || github.ref == 'refs/heads/next'
     permissions:
       contents: write
       issues: write

release.js

@@ -106,7 +106,10 @@ for (const name of packages) {
     nextRelease.notes %>`
 
   const options = {
-    branches: ['latest'],
+    branches: [
+      { name: 'latest' },
+      { name: 'next', channel: 'next', prerelease: true }
+    ],
     tagFormat: name + '-v<%= version %>',
     plugins: [
       wrap(commitAnalyzer),