Automate labeling PRs with obs-ux-management team via GitHub Actions (elastic#220533)

## Summary

We would like to add the `author:obs-ux-management` label to the PRs if
the author of a PR is one of our team members.

I tested this logic in another
[repo](maryam-saeidi/testing#3).

Author: maryam-saeidi

.github/workflows/add-obs-ux-management-author-label.yml

@@ -0,0 +1,43 @@
+name: Add author:obs-ux-management label to PRs
+
+on:
+  pull_request_target:
+    types: [opened]
+
+jobs:
+  label-obs-ux-management-team:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+      contents: read
+
+    steps:
+      - name: Label if author is in the obs-ux-management team
+        uses: actions/github-script@v7
+        with:
+          script: |
+            const obsUxManagementTeam = [
+              "maryam-saeidi",
+              "jasonrhodes",
+              "kdelemme",
+              "mgiota",
+              "shahzad31",
+              "fkanout",
+              "dominiqueclarke",
+              "justinkambic",
+              "cesco-f",
+              "benakansara",
+              "baileycash-elastic"
+            ]; // GitHub usernames
+            const label = "author:obs-ux-management";
+
+            const author = context.payload.pull_request.user.login;
+
+            if (obsUxManagementTeam.includes(author)) {
+              await github.rest.issues.addLabels({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                issue_number: context.payload.pull_request.number,
+                labels: [label],
+              });
+            }