Setup CI. (#5)

diff --git a/.github/workflows/blank.yml b/.github/workflows/blank.yml
new file mode 100644
index 0000000..f55b06c
--- /dev/null
+++ b/.github/workflows/blank.yml
@@ -0,0 +1,15 @@
+name: CI
+
+on:
+  push:
+    branches: [ "master" ]
+  pull_request:
+    branches: [ "**" ]
+
+jobs:
+  ci:
+    runs-on: ubuntu-20.04
+
+    steps:
+      - uses: actions/checkout@v3
+