CI: Validate token XML files against Cockatrice's XSD schema

.github/workflows/validation.yml

@@ -0,0 +1,49 @@
+name: XML Validation
+
+on:
+  push:
+    branches: [ master ]
+    paths:
+      - '.github/workflows/validation.yml'
+      - '**.xml'
+  pull_request:
+    branches: [ master ]
+    paths:
+      - '.github/workflows/validation.yml'
+      - '**.xml'
+  workflow_dispatch:
+  schedule:
+    # Runs at the start of each month (UTC)
+    - cron: '0 0 1 * *'
+
+jobs:
+  validate-xml:
+    name: 'xmllint'
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v3
+
+      - name: Install dependencies
+        run: sudo apt-get install libxml2-utils
+
+      - name: Enable problem matcher
+        uses: korelstar/xmllint-problem-matcher@v1
+
+      - name: Download and validate XSD schema for card database v4
+        id: xsd
+        run: |
+          wget https://www.w3.org/2012/04/XMLSchema.xsd    # Download XSD meta schema to validate xsd files against
+          wget https://raw.githubusercontent.com/Cockatrice/Cockatrice/master/doc/carddatabase_v4/cards.xsd -O carddb_v4.xsd
+          xmllint --noout --schema XMLSchema.xsd carddb_v4.xsd
+
+      - name: Validate tokens.xml
+        if: steps.xsd.outcome == 'success'
+        run: |
+          xmllint --noout --schema carddb_v4.xsd tokens.xml
+
+      - name: Validate challenge_tokens.xml
+        if: steps.xsd.outcome == 'success'
+        run: |
+          xmllint --noout --schema carddb_v4.xsd challenge_tokens.xml

README.md

@@ -1,6 +1,6 @@
 [![Discord](https://img.shields.io/discord/314987288398659595?label=Discord&logo=discord&logoColor=white)](https://discord.gg/3Z9yzmA) [![Gitter Chat](https://img.shields.io/gitter/room/Cockatrice/Magic-Spoiler)](https://gitter.im/Cockatrice/Magic-Spoiler)
 
-Magic-Token [![](https://img.shields.io/badge/dynamic/xml.svg?label=version&url=https%3A%2F%2Fraw.githubusercontent.com%2FCockatrice%2FMagic-Token%2Fmaster%2Ftokens.xml&query=%2F%2FsourceVersion)](https://github.com/Cockatrice/Magic-Token/blob/master/tokens.xml) [![Picture Health](https://github.com/Cockatrice/Magic-Token/actions/workflows/check_links.yml/badge.svg?branch=master)](https://github.com/Cockatrice/Magic-Token/actions/workflows/check_links.yml?query=branch%3Amaster)
+Magic-Token [![](https://img.shields.io/badge/dynamic/xml.svg?label=version&url=https%3A%2F%2Fraw.githubusercontent.com%2FCockatrice%2FMagic-Token%2Fmaster%2Ftokens.xml&query=%2F%2FsourceVersion)](https://github.com/Cockatrice/Magic-Token/blob/master/tokens.xml) [![XML Validation](https://github.com/Cockatrice/Magic-Token/actions/workflows/validation.yml/badge.svg?branch=master)](https://github.com/Cockatrice/Magic-Token/actions/workflows/validation.yml?query=branch%3Amaster) [![Picture Health](https://github.com/Cockatrice/Magic-Token/actions/workflows/check_links.yml/badge.svg?branch=master)](https://github.com/Cockatrice/Magic-Token/actions/workflows/check_links.yml?query=branch%3Amaster)
 =================
 
 This repo contains token information in [Cockatrice](https://github.com/cockatrice/cockatrice)'s [XML card database format](https://github.com/Cockatrice/Cockatrice/wiki/Custom-Cards-&-Sets#to-add-your-own-custom-cards-follow-these-steps) for Magic: The Gathering.<br />
@@ -9,3 +9,7 @@ It describes [![](https://img.shields.io/badge/dynamic/xml.svg?label=&colorB=whi
 For normal tokens, save the file found here: [**tokens.xml**](https://raw.githubusercontent.com/Cockatrice/Magic-Token/master/tokens.xml)
 
 For tokens from the Theros block challege decks, save the file found here: [**challenge_tokens.xml**](https://raw.githubusercontent.com/Cockatrice/Magic-Token/master/challenge_tokens.xml)
+
+<br>
+
+Information & Documentation: https://github.com/Cockatrice/Magic-Token/wiki#documentation

challenge_tokens.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<cockatrice_carddatabase version="4">
+<cockatrice_carddatabase version="4" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://raw.githubusercontent.com/Cockatrice/Cockatrice/master/doc/carddatabase_v4/cards.xsd">
     <sets>
         <set>
             <name>FTH</name>