add compressed-size-action

Author: developit

.github/workflows/main.yml

@@ -0,0 +1,16 @@
+name: Compressed Size
+
+on: [pull_request]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2-beta
+      with:
+        fetch-depth: 1
+    - uses: preactjs/compressed-size-action@v1
+      with:
+        repo-token: "${{ secrets.GITHUB_TOKEN }}"