Add test for checking XML against schema file with xmllint

Author: mkavulich

.github/workflows/pull_request_ci.yml

@@ -8,6 +8,27 @@ on:
       - release/*
 
 jobs:
+  lint-xml:
+    name: Check standard_names.xml against schema file
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Setup Python
+        uses: actions/setup-python@v4
+        with:
+          python-version: "3.x"
+
+      - name: Install dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get -y install libxml2-utils
+
+      - name: Check for duplicate standard names, descriptions
+        run: |
+            xmllint --noout --schema standard_names_v1_0.xsd standard_names.xml
+
   check-unique-standard-names:
     name: Check for duplicates in standard names
     runs-on: ubuntu-latest