Compatible with https://esm.sh

I'm making a cloud playground website that can import any library registered in the NPM registry with `esm.sh`.

By the way, as `esm.sh` has been published for `deno`, it is not possible to import `NodeJS` built-in libraries.

In such reason, this PR removes every direct import statements to the NodeJS built-in libraries, and performed indirect import through `import2` library, so that bundler cannot merge them.

package.json

@@ -6,7 +6,7 @@
     "email": "samchon.github@gmail.com",
     "url": "https://github.com/samchon"
   },
-  "version": "2.5.13",
+  "version": "2.5.16",
   "typings": "./index.d.ts",
   "main": "./index.js",
   "scripts": {

src/exception/index.ts

@@ -26,5 +26,3 @@ export * from "./SystemError";
 export * from "./ErrorCategory";
 export * from "./ErrorCode";
 export * from "./ErrorCondition";
-
-export * from "./global";

src/utility/node.ts

@@ -4,19 +4,30 @@
  * @module std
  */
 //================================================================
-let is_node_: boolean | null = null;
-
 /**
  * Test whether the code is running on NodeJS.
  *
  * @return Whether NodeJS or not.
  */
 export function is_node(): boolean {
     if (is_node_ === null)
-        is_node_ =
-            typeof global === "object" &&
-            typeof global.process === "object" &&
-            typeof global.process.versions === "object" &&
-            typeof global.process.versions.node !== "undefined";
+        is_node_ = typeof global === "object" && is_node_process(global);
     return is_node_;
 }
+
+/**
+ * @internal
+ */
+function is_node_process(m: typeof global | null): boolean {
+    return m !== null && 
+        typeof m.process === "object" && 
+        m.process !== null &&
+        typeof m.process.versions === "object" &&
+        m.process.versions !== null &&
+        typeof m.process.versions.node !== "undefined";
+}
+
+/**
+ * @internal
+ */
+let is_node_: boolean | null = null;