add Dockerfile, compose.yaml

Dockerfile

···
+FROM golang:1.23 AS builder
+WORKDIR /app
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+RUN CGO_ENABLED=0 GOOS=linux go build -o /app/plcwatch
+FROM alpine:latest
+RUN apk --no-cache add ca-certificates
+RUN adduser -D appuser
+USER appuser
+COPY --from=builder /app/plcwatch /plcwatch
+ENTRYPOINT ["/plcwatch"]

compose.yaml

···
+services:
+  app:
+    container_name: plcwatch
+    build:
+      context: .
+      dockerfile: ./Dockerfile