Run workflows on pull requests

Author: matshou

.github/workflows/java-ci.yaml

@@ -8,6 +8,9 @@ on:
   push:
     paths:
       - '**.java'
+  pull_request:
+    paths:
+      - '**.java'
 
 # Continuous integration
 name: Java CI

.github/workflows/java-qa.yaml

@@ -10,6 +10,7 @@ on:
       - 'release/**'        # Release branches
       - 'hotfix/**'         # Hotfix branches
       - master              # Main project branch
+  pull_request:
 
 # Quality Assurance
 name: Java QA