ci: update metanorma workflows and add release manifest

.github/workflows/generate.yml

@@ -0,0 +1,21 @@
+name: generate
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: true
+
+jobs:
+  site:
+    uses: actions-mn/.github/.github/workflows/metanorma-generate.yml@v1
+    secrets: inherit

.github/workflows/release.yml

@@ -0,0 +1,17 @@
+name: Release
+
+on:
+  push:
+    branches: [main]
+    paths: ['sources/**', 'metanorma.yml', 'metanorma.release.yml']
+  workflow_dispatch:
+
+permissions:
+  contents: write
+
+jobs:
+  release:
+    uses: actions-mn/.github/.github/workflows/metanorma-release.yml@v1
+    with:
+      default-visibility: private
+    secrets: inherit