standalone XML files

[avdland]

The plugin complains about the embedded DTD end tag:
line XX:XX extraneous input '\n]>\n\n' expecting {COMMENT, SEA_WS, '<', PI}

example of the XML file:

<?xml version="1.0" standalone="yes" ?>

<!--open the DOCTYPE declaration -
  the open square bracket indicates an internal DTD-->
<!DOCTYPE foo [

<!--define the internal DTD-->
  <!ELEMENT foo (#PCDATA)>

<!--close the DOCTYPE declaration-->
]>

<foo>Hello World.</foo>

[ppalaga]

This an issue of the XML linter in https://github.com/ec4j/editorconfig-linters/blob/main/editorconfig-linters/src/main/java/org/ec4j/linters/XmlLinter.java
It would be great to add a test to https://github.com/ec4j/editorconfig-linters/blob/main/editorconfig-linters/src/test/java/org/ec4j/linters/XmlLinterTest.java and fix the issue of course. Contributions welcome!