Support XML encoding with UTF-8 including BOM field (#491)

core.js

@@ -1066,6 +1066,13 @@ async function _fromTokenizer(tokenizer) {
 		};
 	}
 
+	if (check([0xEF, 0xBB, 0xBF]) && checkString('<?xml', {offset: 3})) { // UTF-8-BOM
+		return {
+			ext: 'xml',
+			mime: 'application/xml',
+		};
+	}
+
 	// -- 9-byte signatures --
 
 	if (check([0x49, 0x49, 0x52, 0x4F, 0x08, 0x00, 0x00, 0x00, 0x18])) {

fixture/fixture-utf8-bom.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-16"?>
+<FileType>
+	<encoding>UTF-8 with BOM</encoding>
+</FileType>

test.js

@@ -206,6 +206,10 @@ const names = {
 	webm: [
 		'fixture-null', // EBML DocType with trailing null character
 	],
+	xml: [
+		'fixture',
+		'fixture-utf8-bom', // UTF-8 with BOM
+	],
 };
 
 // Define an entry here only if the file type has potential