Fix 'frontend' currently not working (to LTS)

Fix the alpine base image since the npm version has a newer major version. Fi to LTS version 18. See issue: open-telemetry#601

src/frontend/Dockerfile

@@ -1,12 +1,12 @@
-FROM node:19.1-alpine AS deps
+FROM node:18-alpine AS deps
 RUN apk add --no-cache libc6-compat
 
 WORKDIR /app
 
 COPY ./src/frontend/package*.json ./
 RUN npm ci
 
-FROM node:19.1-alpine AS builder
+FROM node:18-alpine AS builder
 RUN apk add --no-cache libc6-compat protobuf-dev protoc
 WORKDIR /app
 COPY --from=deps /app/node_modules ./node_modules
@@ -16,7 +16,7 @@ COPY ./src/frontend .
 RUN npm run grpc:generate
 RUN npm run build
 
-FROM node:19.1-alpine AS runner
+FROM node:18-alpine AS runner
 WORKDIR /app
 RUN apk add --no-cache protoc