CheckstyleConfigLoader does not support JavadocStyle - checkFirstSentence

While not all of JavadocStyle can be fixed checkFirstSentence can be

https://checkstyle.sourceforge.io/apidocs/com/puppycrawl/tools/checkstyle/checks/javadoc/JavadocStyleCheck.html

        <module name="JavadocStyle">
            <property name="severity" value="${checkstyle.javadocstyle.severity}" default="warning"/>
            <property name="scope" value="${checkstyle.javadocstyle.scope}" default="public"/>
            <property name="checkFirstSentence" value="${checkstyle.javadocstyle.checkfirstsentence}" default="true"/>
            <property name="checkEmptyJavadoc" value="${checkstyle.javadocstyle.checkemptyjavadoc}" default="true"/>
            <property name="checkHtml" value="${checkstyle.javadocstyle.checkhtml}" default="true"/>
            <property name="tokens" value="${checkstyle.javadocstyle.tokens}" default="ANNOTATION_DEF, ANNOTATION_FIELD_DEF, CLASS_DEF, CTOR_DEF, ENUM_CONSTANT_DEF, ENUM_DEF, INTERFACE_DEF, METHOD_DEF, PACKAGE_DEF, VARIABLE_DEF"/>
        </module>

Start at CheckstyleConfigLoader, the entry point named in the issue, and compare its JavadocStyle handling with the Checkstyle JavadocStyleCheck documentation linked above. Verify the loader accepts the checkFirstSentence property and add or update coverage for that configuration; done means the property is supported without breaking existing JavadocStyle options.