feat: replace gitlab-ci by github actions

.github/workflows/pages.yml

@@ -0,0 +1,26 @@
+name: Pages deployment
+
+on:
+  push:
+
+jobs:
+  deploy:
+    runs-on: ubuntu-20.04
+    concurrency:
+      group: ${{ github.workflow }}-${{ github.ref }}
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Setup mdBook
+        uses: peaceiris/actions-mdbook@v1
+        with:
+          mdbook-version: '0.4.10'
+
+      - run: mdbook build
+
+      - name: Deploy
+        uses: peaceiris/actions-gh-pages@v3
+        if: ${{ github.ref == 'refs/heads/github' }}
+        with:
+          github_token: ${{ secrets.GITHUB_TOKEN }}
+          publish_dir: ./out/html

.github/workflows/pandoc.yml

@@ -0,0 +1,73 @@
+name: Pandoc
+
+on: push
+
+jobs:
+  pdf:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: create file list
+        id: files_list
+        run: |
+          mkdir output
+          echo "::set-output name=files::$(printf '"%s" ' src/??-*.md)"
+      - uses: docker://pandoc/latex:2.9
+        with:
+          args: >-
+            --resource-path src
+            --toc --toc-depth=2
+            --webtex
+            -f markdown --pdf-engine=xelatex --listings
+            --metadata-file=metadata.pandoc.yml
+            --output=output/result.pdf
+            ${{ steps.files_list.outputs.files }}
+      - uses: actions/upload-artifact@master
+        with:
+          name: pdf
+          path: output
+  docx:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: create file list
+        id: files_list
+        run: |
+          mkdir output
+          echo "::set-output name=files::$(printf '"%s" ' src/??-*.md)"
+      - uses: docker://pandoc/core:2.9
+        with:
+          args: >-
+            --resource-path src
+            --toc --toc-depth=2
+            --webtex
+            --metadata-file=metadata.pandoc.yml
+            --output=output/result.docx
+            ${{ steps.files_list.outputs.files }}
+      - uses: actions/upload-artifact@master
+        with:
+          name: docx
+          path: output
+  epub:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: create file list
+        id: files_list
+        run: |
+          mkdir output
+          echo "::set-output name=files::$(printf '"%s" ' src/??-*.md)"
+      - uses: docker://pandoc/core:2.9
+        with:
+          args: >-
+            --resource-path src
+            --toc --toc-depth=2
+            --webtex
+            --epub-cover-image=src/images/cover.png
+            --metadata-file=metadata.pandoc.yml
+            --output=output/result.epub
+            ${{ steps.files_list.outputs.files }}
+      - uses: actions/upload-artifact@master
+        with:
+          name: epub
+          path: output