CI: update for current best practices

Author: ctrueden

Diff for: .github/workflows/build-pr.yml

@@ -6,6 +6,9 @@ on:
       - master
     tags:
       - "*-[0-9]+.*"
+  pull_request:
+    branches:
+      - master
 
 jobs:
   build:
@@ -28,5 +31,6 @@ jobs:
           GPG_PASSPHRASE: ${{ secrets.GPG_PASSPHRASE }}
           MAVEN_USER: ${{ secrets.MAVEN_USER }}
           MAVEN_PASS: ${{ secrets.MAVEN_PASS }}
+          OSSRH_USER: ${{ secrets.OSSRH_USER }}
           OSSRH_PASS: ${{ secrets.OSSRH_PASS }}
           SIGNING_ASC: ${{ secrets.SIGNING_ASC }}