Docs: add Dockerfile for docs (#369)

Signed-off-by: Carson Yang <yangchuansheng33@gmail.com>

.github/workflows/docs-image.yml

+name: Build FastGPT docs images and copy image to docker hub
+on:
+  workflow_dispatch:
+  push:
+    paths:
+      - 'docSite/**'
+    branches:
+      - 'main'
+    tags:
+      - 'v*.*.*'
+jobs:
+  build-fastgpt-images:
+    runs-on: ubuntu-20.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 1
+      - name: Set up QEMU (optional)
+        uses: docker/setup-qemu-action@v2
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+        with:
+          driver-opts: network=host
+      - name: Cache Docker layers
+        uses: actions/cache@v2
+        with:
+          path: /tmp/.buildx-cache
+          key: ${{ runner.os }}-buildx-${{ github.sha }}
+          restore-keys: |
+            ${{ runner.os }}-buildx-
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v2
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GH_PAT }}
+      - name: Set DOCKER_REPO_TAGGED based on branch or tag
+        run: |
+          if [[ "${{ github.ref_name }}" == "main" ]]; then
+            echo "DOCKER_REPO_TAGGED=ghcr.io/${{ github.repository_owner }}/fastgpt-docs:latest" >> $GITHUB_ENV
+          else
+            echo "DOCKER_REPO_TAGGED=ghcr.io/${{ github.repository_owner }}/fastgpt-docs:${{ github.ref_name }}" >> $GITHUB_ENV
+          fi
+      - name: Build and publish image for main branch or tag push event
+        env:
+          DOCKER_REPO_TAGGED: ${{ env.DOCKER_REPO_TAGGED }}
+        run: |
+          docker buildx build \
+          --build-arg name=app \
+          --platform linux/amd64,linux/arm64 \
+          --label "org.opencontainers.image.source=  https://github.com/  ${{ github.repository_owner }}/FastGPT" \
+          --label "org.opencontainers.image.description=fastgpt image" \
+          --label "org.opencontainers.image.licenses=Apache" \
+          --push \
+          --cache-from=type=local,src=/tmp/.buildx-cache \
+          --cache-to=type=local,dest=/tmp/.buildx-cache \
+          -t ${DOCKER_REPO_TAGGED} \
+          -f docSite/Dockerfile \
+          .
+  push-to-docker-hub:
+    needs: build-fastgpt-images
+    runs-on: ubuntu-20.04
+    if: github.repository == 'labring/FastGPT'
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+      - name: Login to Docker Hub
+        uses: docker/login-action@v2
+        with:
+          username: ${{ secrets.DOCKER_HUB_NAME }}
+          password: ${{ secrets.DOCKER_HUB_PASSWORD }}
+      - name: Set DOCKER_REPO_TAGGED based on branch or tag
+        run: |
+          if [[ "${{ github.ref_name }}" == "main" ]]; then
+            echo "IMAGE_TAG=latest" >> $GITHUB_ENV
+          else
+            echo "IMAGE_TAG=${{ github.ref_name }}" >> $GITHUB_ENV
+          fi
+      - name: Pull image from GitHub Container Registry
+        run: docker pull ghcr.io/${{ github.repository_owner }}/fastgpt-docs:${{env.IMAGE_TAG}}
+      - name: Tag image with Docker Hub repository name and version tag
+        run: docker tag ghcr.io/${{ github.repository_owner }}/fastgpt-docs:${{env.IMAGE_TAG}} ${{ secrets.DOCKER_IMAGE_NAME }}:${{env.IMAGE_TAG}}
+      - name: Push image to Docker Hub
+        run: docker push ${{ secrets.DOCKER_IMAGE_NAME }}:${{env.IMAGE_TAG}}
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docSite/Dockerfile

+FROM hugomods/hugo:0.117.0 AS builder
+
+WORKDIR /app
+
+ADD ./docSite hugo
+RUN cd /app/hugo && hugo mod get -u github.com/colinwilson/lotusdocs && hugo -v --minify
+
+FROM fholzer/nginx-brotli:latest
+
+LABEL org.opencontainers.image.source https://github.com/labring/FastGPT
+
+COPY --from=builder /app/hugo/public /usr/share/nginx/html
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