ConfigDocument seems to break include required() statements

[mikehearn]

The following test fails:

        val doc = ConfigDocumentFactory.parseString("""
            include required("a.conf")
            include required("b.conf")
            
            abc = 1
        """.trimIndent())
        val result = doc.withValueText("abc", "2").render()
        assertEquals("""
            include required("a.conf")
            include required("b.conf")
            
            abc = 2            
        """.trimIndent(), result)

The problem is the closing bracket gets chopped - you end up with:

include required("a.conf"
include required("b.conf"