JS: add test case

javascript/ql/test/library-tests/ModuleImportNodes/CustomImport.expected

@@ -0,0 +1 @@
+| fs | fs | customImport.js:1:12:1:29 | customImport("fs") |

javascript/ql/test/library-tests/ModuleImportNodes/CustomImport.ql

@@ -0,0 +1,15 @@
+import javascript
+
+class CustomImport extends DataFlow::ModuleImportNode::Range, DataFlow::CallNode {
+  CustomImport() {
+    getCalleeName() = "customImport"
+  }
+
+  override string getPath() {
+    result = getArgument(0).getStringValue()
+  }
+}
+
+from string path, CustomImport imprt
+where imprt = DataFlow::moduleImport(path)
+select path, imprt.getPath(), imprt

javascript/ql/test/library-tests/ModuleImportNodes/customImport.js

@@ -0,0 +1 @@
+const fs = customImport("fs");