Added Docker and nginx config

Dockerfile

+FROM node:14.16-alpine3.13 as build
+WORKDIR /app
+ENV PATH /app/node_modules/.bin:$PATH
+COPY . .
+RUN yarn
+RUN yarn build
+
+FROM nginx:stable-alpine
+COPY --from=build /app/build /usr/share/nginx/html
+COPY --from=build /app/nginx/nginx.conf /etc/nginx/conf.d/default.conf
+EXPOSE 80
+CMD ["nginx", "-g", "daemon off;"]

nginx/nginx.conf

+server {
+listen 80;
+location / {
+root /usr/share/nginx/html;
+index index.html index.htm;
+try_files $uri $uri/ /index.html =404;
+}
+}