build: update Checkstyle container image version

.gitea/workflows/ci.yml

@@ -8,7 +8,7 @@ jobs:
     name: "Checkstyle Main"
     runs-on: "vps-4"
     container:
-      image: "cimg/openjdk:21.0-node"
+      image: "cimg/openjdk:22.0-node"
     steps:
       - name: "Checkout"
         uses: actions/checkout@v3

backend/config/checkstyle/checkstyle.xml

@@ -0,0 +1,23 @@
+<?xml version="1.0"?>
+<!DOCTYPE module PUBLIC
+        "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
+        "https://checkstyle.org/dtds/configuration_1_3.dtd"
+        >
+<module name="Checker">
+    <module name="SuppressionFilter">
+        <property name="file" value="${config_loc}/checkstyle-ignore.xml"/>
+    </module>
+
+    <property name="severity" value="error"/>
+    <property name="tabWidth" value="4"/>
+
+    <module name="LineLength">
+        <property name="max" value="500"/>
+    </module>
+    <module name="FileTabCharacter">
+        <property name="eachLine" value="true"/>
+    </module>
+
+    <module name="NewlineAtEndOfFile"/>
+
+</module>