Update Docker configs

This commit updates the Dockerfile so that the image is built on top of the nodejs Long-term support (LTS) version. Manually bumping the nodejs version is no longer required.

Additionally, the ports definition in docker-compose.yml is quoted as string, as suggested in the reference documentation.

Dockerfile

@@ -1,4 +1,4 @@
-FROM node:10-buster as build
+FROM node:lts as build
 RUN mkdir /tmp/brouter-web
 WORKDIR /tmp/brouter-web
 COPY . .

docker-compose.yml

@@ -7,7 +7,7 @@ services:
         command: yarn serve
         image: node:lts
         ports:
-            - 3000:3000
+            - '3000:3000'
         user: '1000'
         volumes:
             - ./:/src