[Misc] Added workflow to check each pull request

Summary: Added following checks:
- Commit format checking, using dragonwell-releng/check_commit_action@master.
- Build and run sanity test in release and slowdebug mode.

Test Plan: checks shipped with this PR

Reviewed-by: yuleil, kuaiwei

Issue: #11

.github/workflows/check_pr.yml

+#
+# Copyright (c) 2019 Alibaba Group Holding Limited. All Rights Reserved.
+# DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+#
+# This code is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License version 2 only, as
+# published by the Free Software Foundation. Alibaba designates this
+# particular file as subject to the "Classpath" exception as provided
+# by Oracle in the LICENSE file that accompanied this code.
+#
+# This code is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+# version 2 for more details (a copy is included in the LICENSE file that
+# accompanied this code).
+#
+# You should have received a copy of the GNU General Public License version
+# 2 along with this work; if not, write to the Free Software Foundation,
+# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+#
+
+name: Dragonwell_11_build_test
+
+on: [pull_request]
+
+jobs:
+  check_commit:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: dragonwell-releng/check_commit_action@master
+
+  build_release_jdk:
+    runs-on: ubuntu-latest
+    container:
+      image: docker.io/dragonwelljdk/build_jdk:11u
+    steps:
+      - uses: actions/checkout@v2
+      - name: Compile release mode
+        run: |
+          chmod 755 configure
+          bash make.sh release
+
+      - name: Sanity test
+        run: |
+          TEST_JDK_HOME=build/linux-x86_64-normal-server-release/images/jdk
+          ${TEST_JDK_HOME}/bin/java -version
+
+  build_slowdebug_jdk:
+    runs-on: ubuntu-latest
+    container:
+      image: docker.io/dragonwelljdk/build_jdk:11u
+    steps:
+      - uses: actions/checkout@v2
+      - name: Compile slowdebug mode
+        run: |
+          chmod 755 configure
+          bash make.sh debug
+
+      - name: Sanity test
+        run: |
+          TEST_JDK_HOME=build/linux-x86_64-normal-server-slowdebug/images/jdk
+          ${TEST_JDK_HOME}/bin/java -version