update docker instructions, fixes #278

Dockerfile.build

@@ -0,0 +1,11 @@
+FROM node:lts AS builder
+ARG BASE_PATH=./
+WORKDIR /src
+COPY . /src
+RUN yarn config set enableTelemetry 0 && \
+    yarn install --immutable --network-timeout=300000 && \
+    yarn build --base=$BASE_PATH
+
+FROM ghcr.io/static-web-server/static-web-server:2
+ENV SERVER_ROOT=/app
+COPY --from=builder /src/dist /app