ci: switch to github actions for build, disable travis

.github/workflows/buildapp.yaml

@@ -1,6 +1,9 @@
-name: Build/release
+name: Build ReplayWeb.page App
 
-on: push
+on:
+  push:
+    branches:
+      - main
 
 jobs:
   release:
@@ -8,10 +11,10 @@ jobs:
 
     strategy:
       matrix:
-        os: [macos-latest, ubuntu-latest]
+        os: [macos-10.14, ubuntu-latest]
         platform: [windows, linux]
         exclude:
-          - os: macos-latest
+          - os: macos-10.14
             platform: windows
 
     steps: