ci: Deploy pages (#703)

## fixes KILTprotocol/ticket#3583
Deploys master as default docs branch then each tag and develop are put
inside the root directory
Succeful deployment can be seen here
/~https://github.com/KILTprotocol/kilt-node/actions/runs/10595010314

## Metadata Diff to Develop Branch

<details>
<summary>Peregrine Diff</summary>

```
```

</details>

<details>
<summary>Spiritnet Diff</summary>

```
```

</details>

## Checklist:

- [ ] I have verified that the code works
- [ ] No panics! (checked arithmetic ops, no indexing `array[3]` use
`get(3)`, ...)
- [ ] I have verified that the code is easy to understand
  - [ ] If not, I have left a well-balanced amount of inline comments
- [ ] I have [left the code in a better
state](https://deviq.com/principles/boy-scout-rule)
- [ ] I have documented the changes (where applicable)
* Either PR or Ticket to update [the
Docs](/~https://github.com/KILTprotocol/docs)
    * Link the PR/Ticket here

---------

Co-authored-by: Antonio Antonino <antonio@kilt.io>

.github/workflows/publish-rustdocs.yml

@@ -11,19 +11,30 @@ on:
     types:
       - completed
 
+permissions:
+  contents: write
+  pages: write
+  id-token: write
+
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref_name }}
   cancel-in-progress: true
 
 jobs:
-  deploy-rustdocs:
-    name: Deploy rustdoc
+  build-rustdoc:
+    name: Build rustdoc
     runs-on: ubuntu-latest
     env:
       DOCS_TARGET: target/doc
+      BRANCH: gh-pages
     if: ${{ github.event_name == 'workflow_dispatch' || (github.event_name == 'workflow_run' && github.event.workflow_run.conclusion == 'success') }}
 
     steps:
+      - name: Free Disk Space
+        uses: jlumbroso/free-disk-space@main
+        with:
+          tool-cache: true
+
       - name: Checkout repository
         uses: actions/checkout@v4
 
@@ -42,13 +53,51 @@ jobs:
           docker run --rm \
             -v "${GITHUB_WORKSPACE}:/workspace" \
             -v "${HOME}/.cargo:/root/.cargo" \
-            -w /workspace \
             -e RUSTDOCFLAGS='-D warnings' \
+            -w /workspace \
             paritytech/ci-unified:bullseye-1.74.0 \
-            bash -c "cargo doc --all-features --no-deps --locked && chown -R $(id -u):$(id -g) ${{ env.DOCS_TARGET }}"
+            bash -c "
+              cargo doc --all-features --no-deps --locked && \
+              mv $DOCS_TARGET/help.html $DOCS_TARGET/index.html && \
+              chown -R $(id -u):$(id -g) $DOCS_TARGET"
 
-      - name: Deploy to GitHub Pages
+      - name: Set target folder for non-master branches
+        if: github.ref_name != 'master'
+        run: echo "TARGET_FOLDER=${{ github.ref_name }}" >> $GITHUB_ENV
+
+      - name: Push to gh-pages branch
         uses: JamesIves/github-pages-deploy-action@v4
         with:
-          branch: gh-pages-${{ github.ref_name }}
+          branch: ${{ env.BRANCH }}
           folder: ${{ env.DOCS_TARGET }}
+          target-folder: ${{ env.TARGET_FOLDER }}
+
+
+  deploy-rustdoc:
+    name: Deploy rustdoc
+    environment:
+      name: gh-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    runs-on: ubuntu-latest
+    needs: build-rustdoc
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          ref: gh-pages
+
+      - name: Setup Pages
+        uses: actions/configure-pages@v5
+
+      - name: Build with Jekyll
+        uses: actions/jekyll-build-pages@v1
+        with:
+          source: ./
+          destination: ./_site
+
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4