Add reusable workflows for PRs and testing builds

.github/workflows/pr.yml

@@ -0,0 +1,9 @@
+name: PR
+
+on:
+    pull_request:
+        branches: [ master ]
+
+jobs:
+    call-pr-workflow:
+        uses: FossifyOrg/.github/.github/workflows/pr.yml@main

.github/workflows/testing-build.yml

@@ -0,0 +1,10 @@
+name: Testing build (on PR)
+
+on:
+    pull_request:
+        branches: [ master ]
+        types: [ labeled, opened, synchronize, reopened ]
+
+jobs:
+    call-testing-build-workflow:
+        uses: FossifyOrg/.github/.github/workflows/testing-build.yml@main