chore: enable CI on pulls (#89)

Author: Gozala

.github/workflows/main.yml

@@ -1,5 +1,5 @@
 name: ci
-on: [push]
+on: [push, pull_request]
 
 jobs:
   check:
@@ -56,4 +56,4 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - run: yarn
-      - run: npx xvfb-maybe yarn aegir test -t electron-renderer --bail
+      - run: npx xvfb-maybe yarn aegir test -t electron-renderer --bail