Moving to node_modules folder to make easier to upgrade

trying to move from Bootstrap 3 to Bootstrap 5

node_modules/is-function/index.js

@@ -0,0 +1,18 @@
+module.exports = isFunction
+
+var toString = Object.prototype.toString
+
+function isFunction (fn) {
+  if (!fn) {
+    return false
+  }
+  var string = toString.call(fn)
+  return string === '[object Function]' ||
+    (typeof fn === 'function' && string !== '[object RegExp]') ||
+    (typeof window !== 'undefined' &&
+     // IE8 and below
+     (fn === window.setTimeout ||
+      fn === window.alert ||
+      fn === window.confirm ||
+      fn === window.prompt))
+};