[JS] Add a doc comment for SourceMapLocationRemapper

js/js.parser/src/org/jetbrains/kotlin/js/parser/sourcemaps/SourceMapLocationRemapper.kt

@@ -18,6 +18,11 @@ package org.jetbrains.kotlin.js.parser.sourcemaps
 
 import org.jetbrains.kotlin.js.backend.ast.*
 
+/**
+ * JS source map remapper takes parsed source maps
+ * together with JS AST with correct JS positioning information
+ * and converts the latter into Kotlin positioning information
+ */
 class SourceMapLocationRemapper(private val sourceMap: SourceMap, private val sourceMapPathMapper: (String) -> String = { it }) {
     fun remap(node: JsNode) {
         val listCollector = JsNodeFlatListCollector()
@@ -138,4 +143,4 @@ class SourceMapLocationRemapper(private val sourceMap: SourceMap, private val so
             return first.startLine > second.startLine || (first.startLine == second.startLine && first.startChar >= second.startChar)
         }
     }
-}
+}