update and split docs

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

docs/advanced/standalone.md

@@ -0,0 +1,29 @@
+# Standalone mode
+
+If you don't have the Docker CLI installed on the GitHub Runner, Buildx binary
+is invoked directly, instead of calling it as a docker plugin. This can be
+useful if you want to use the `kubernetes` driver in your self-hosted runner:
+
+```yaml
+name: ci
+
+on:
+  push:
+
+jobs:
+  buildx:
+    runs-on: ubuntu-latest
+    steps:
+      -
+        name: Checkout
+        uses: actions/checkout@v3
+      -
+        name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+        with:
+          driver: kubernetes
+      -
+        name: Build
+        run: |
+          buildx build .
+```