includes -> indexof for node 4

Author: Maxim-Mazurok

src/ExportMap.js

@@ -548,7 +548,7 @@ ExportMap.parse = function (path, content, context) {
     isEsModuleInteropTrue && exports.push('TSNamespaceExportDeclaration')
 
     // This doesn't declare anything, but changes what's being exported.
-    if (exports.includes(n.type)) {
+    if (exports.indexOf(n.type) !== -1) {
       const exportedName = n.expression && n.expression.name || n.id.name
       const declTypes = [
         'VariableDeclaration',
@@ -561,7 +561,7 @@ ExportMap.parse = function (path, content, context) {
         'TSModuleDeclaration',
       ]
       const exportedDecls = ast.body.filter(({ type, id, declarations }) => 
-        declTypes.includes(type) && 
+        declTypes.indexOf(type) !== -1 && 
         (
           (id && id.name === exportedName) ||
           (declarations && declarations.find(d => d.id.name === exportedName))