Add Dockerized OpenTofu runner

docker/opentofu/Dockerfile

@@ -0,0 +1,18 @@
+ARG OPENTOFU_VERSION=1.10
+
+FROM ghcr.io/opentofu/opentofu:${OPENTOFU_VERSION}-minimal AS opentofu
+
+FROM alpine:3.22
+
+RUN apk add --no-cache \
+    bash \
+    ca-certificates \
+    curl \
+    git \
+    openssh-client
+
+COPY --from=opentofu /usr/local/bin/tofu /usr/local/bin/tofu
+
+WORKDIR /workspace
+
+ENTRYPOINT ["tofu"]