Update README image syntax and modify ROAMJS_PROXY environment variable in workflow

Author: mdroidian

.github/workflows/main.yaml

@@ -14,7 +14,7 @@ env:
   AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
   AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
   AWS_REGION: ${{ vars.AWS_REGION }}
-  ROAMJS_PROXY: ${{ vars.ROAMJS_PROXY }}
+  ROAMJS_PROXY: RoamJS
 
 jobs:
   deploy: