Add addition yml extension

CHANGES.txt

@@ -1,4 +1,5 @@
 Current
+New: Added .yml file extension for yaml suite files, previously only .yaml was allowed for yaml (Steven Jubb)
 Fixed: GITHUB-2770: FileAlreadyExistsException when report is generated (melloware)
 Fixed: GITHUB-2825: Programically Loading TestNG Suite from JAR File Fails to Delete Temporary Copy of Suite File (Steven Jubb)
 Fixed: GITHUB-2818: Add configuration key for callback discrepancy behavior (Krishnan Mahadevan)

testng-core/src/main/java/org/testng/Converter.java

@@ -65,7 +65,7 @@ private void run(String[] args) throws IOException {
           if (file.endsWith(".xml")) {
             File newFile = new File(m_outputDirectory, baseName + ".yaml");
             writeFile(newFile, Yaml.toYaml(suite).toString());
-          } else if (file.endsWith(".yaml")) {
+          } else if (file.endsWith(".yaml") || file.endsWith(".yml")) {
             File newFile = new File(m_outputDirectory, baseName + ".xml");
             writeFile(newFile, suite.toXml());
           } else {

testng-core/src/main/java/org/testng/internal/YamlParser.java

@@ -21,6 +21,7 @@ public XmlSuite parse(String filePath, InputStream is, boolean loadClasses)
 
   @Override
   public boolean accept(String fileName) {
-    return Parser.hasFileScheme(fileName) && fileName.endsWith(".yaml");
+    return Parser.hasFileScheme(fileName) && fileName.endsWith(".yaml")
+        || fileName.endsWith(".yml");
   }
 }