edit README

README.md

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 # gitea-act-runner-buildx
 
 Gitea Action Runner with buildx
+
+How to use:
+1. Enable binfmt/QEMU local
+    -> docker run --rm --privileged tonistiigi/binfmt --install all
+
+2. Check
+    -> ls /proc/sys/fs/binfmt_misc
+
+3. Start Runner via docker run or docker compose
+
+4. In your workflow add this to setup the multiarch-builder
+
+- name: Setup buildx multiarch
+  run: |
+    docker buildx create \
+      --name multiarch \
+      --driver docker-container \
+      --use || docker buildx use multiarch