fix: fix npm build step

OliverBooth/Dockerfile

@@ -1,11 +1,3 @@
-# run Gulp to build the app
-FROM node:12.16.1-alpine as build-stage
-COPY package*.json ./
-COPY Gulpfile.js ./
-RUN npm install --global gulp-cli
-RUN npm install
-RUN gulp
-
 FROM mcr.microsoft.com/dotnet/aspnet:7.0 AS base
 WORKDIR /app
 EXPOSE 80
@@ -16,6 +8,14 @@ WORKDIR /src
 COPY ["OliverBooth/OliverBooth.csproj", "OliverBooth/"]
 RUN dotnet restore "OliverBooth/OliverBooth.csproj"
 COPY . .
+
+RUN apt-get update && apt-get install -y curl
+RUN curl -sL https://deb.nodesource.com/setup_20.x | bash -
+RUN apt-get install -y nodejs
+RUN npm i -g gulp-cli
+RUN npm i
+RUN gulp
+
 WORKDIR "/src/OliverBooth"
 RUN dotnet build "OliverBooth.csproj" -c Release -o /app/build