Run syntax tests when grammar changes

.github/workflows/syntax.yml

@@ -0,0 +1,28 @@
+name: Run syntax tests
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'syntaxes/**'
+  pull_request:
+    branches:
+      - main
+    paths:
+      - 'syntaxes/**'
+
+jobs:
+  syntax:
+    runs-on: ubuntu-latest
+    timeout-minutes: 3
+    steps:
+      - name: Checkout Repo
+        uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+        with:
+          node-version-file: '.nvmrc'
+      - name: npm install
+        run: npm ci
+      - name: syntax
+        run: npm run test:syntax

.github/workflows/test.yml

@@ -23,20 +23,6 @@ jobs:
       - name: lint
         run: npm run lint
 
-  syntax:
-    runs-on: ubuntu-latest
-    timeout-minutes: 3
-    steps:
-      - name: Checkout Repo
-        uses: actions/checkout@v2
-      - uses: actions/setup-node@v2
-        with:
-          node-version-file: '.nvmrc'
-      - name: npm install
-        run: npm ci
-      - name: syntax
-        run: npm run test:syntax
-
   unit:
     strategy:
       fail-fast: false