SpringHeader check with regexp is not valid

[snicoll]

The checkstyle-header.txt in the project does not seem to be a valid regexp:

java.util.regex.PatternSyntaxException: Illegal/unsupported escape sequence near index 12
        ^\Q^\Q/*\E$\E$

(the index might not be exact)

Also, this file is ignored. To use it, you need to patch the checkstyle configuration as follows:

<module name="io.spring.javaformat.checkstyle.SpringChecks">
	<property name="headerFile" value="${config_loc}/checkstyle-header.txt"/>
</module>