ICU-23056 Run CI for exhaustive tests on PRs that update resource files

.github/workflows/icu_exhaustive_tests.yml

diff --git a/.github/workflows/icu_exhaustive_tests.yml b/.github/workflows/icu_exhaustive_tests.yml
index 8d0b11a..7cdb77c 100644
--- a/.github/workflows/icu_exhaustive_tests.yml
+++ b/.github/workflows/icu_exhaustive_tests.yml
@@ -21,6 +21,12 @@
       - 'icu4j/**'
       - 'testdata/**'
       - '.github/workflows/**'
+  # run exhaustive texts on PRs that modify resource files
+  pull_request:
+    branches: '**'
+    paths:
+      - 'icu4c/source/data/**'
+      - 'icu4j/**/src/main/resources/com/ibm/icu/impl/data/icudata/**'
   schedule:
     # Runs daily on default branch (main) only.
     # https://docs.github.com/en/actions/writing-workflows/choosing-when-your-workflow-runs/events-that-trigger-workflows#schedule