refactor(ci): use GitHub actions instead of CircleCI

.github/workflows/pull-request-ci.yml

@@ -0,0 +1,42 @@
+name: Pull request workflow
+
+on:
+  pull_request:
+
+jobs:
+  pr:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions/setup-node@v1
+        with:
+          node-version: '12'
+      - name: Get yarn cache directory path
+        id: yarn-cache-dir-path
+        run: echo "::set-output name=dir::$(yarn cache dir)"
+      - uses: actions/cache@v1
+        with:
+          path: ${{ steps.yarn-cache-dir-path.outputs.dir }}
+          key: ${{ runner.os }}-node-modules-${{ hashFiles('yarn.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-node-modules-
+            ${{ runner.os }}-
+
+      - name: Install dependencies
+        if: steps.yarn-cache.outputs.cache-hit != 'true'
+        run: yarn
+
+      - name: Run tsc
+        run: yarn tsc
+
+      - name: Run unit tests
+        run: yarn test
+
+      - name: Check linter
+        run: yarn lint
+
+      - name: Check markdown linter
+        run: yarn workspace docs lint-md
+
+      - name: Build vuepress
+        run: yarn build