chore(docker): add base_path to build args

Dockerfile

@@ -1,6 +1,8 @@
 # Build image
 FROM node:12.18-alpine AS build
+ARG BASE_PATH
 ARG DATABASE_TYPE
+ENV BASE_PATH=$BASE_PATH
 ENV DATABASE_URL "postgresql://umami:umami@db:5432/umami" \
     DATABASE_TYPE=$DATABASE_TYPE
 WORKDIR /build