GitHub Actions (#2)

* add workflow

* fix: add @master

* fix: test

* fix

* onpush

* fix paths

* add badge

.github/workflows/web.yml

@@ -0,0 +1,17 @@
+name: Web App
+on:
+  push:
+    paths:
+      - web/*
+  pull_request:
+    paths:
+      - web/*
+jobs:
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/setup-node@master
+      - uses: actions/checkout@master
+      - run: yarn --cwd web install
+      - run: yarn --cwd web test