ci(deploy-docs): enable on PR without uploads

Author: rami3l

.github/workflows/deploy-docs.yaml

@@ -1,6 +1,7 @@
 name: Deploy Docs
 
 on:
+  pull_request:
   push:
     branches:
       - stable
@@ -43,6 +44,7 @@ jobs:
           mdbook build
           mv book ${{ runner.temp }}/book/dev-guide
       - name: Deploy to GitHub
+        if: ${{ github.event_name != 'pull_request' }}
         run: |
           cd ${{ runner.temp }}/book
           git init