pre-commit: add XML check

.pre-commit-config.yaml

@@ -59,3 +59,11 @@ repos:
         files: \.(po|ttc)$
         entry: make font-update
         pass_filenames: false
+
+  - repo: local
+    hooks:
+      - id: xml
+        name: xml
+        language: system
+        entry: xmllint --noout
+        files: \.(gdxui|tsx|tmx|xml|loc|its)$

Dockerfile

@@ -6,6 +6,7 @@ RUN apt-get update \
         gettext \
         git \
         imagemagick \
+        libxml2-utils \
         make \
         openjdk-11-jdk \
         python3-pip \