Fix CI (#31)

Author: fregante

.github/workflows/main.yml

@@ -9,19 +9,28 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+        with:
+          node-version: 16
       - run: npm install
       - run: npx xo
 
   Types:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+        with:
+          node-version: 16
       - run: npm install
       - run: npx tsd
 
   Test:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+        with:
+          node-version: 16
       - run: npm install
       - run: npx ava