feat: Refactor server implementation to support Bun and Node environments

- Introduced `ServerNode` and `BunServer` classes to handle server logic for Node and Bun respectively.
- Updated `App` class to initialize the appropriate server based on the runtime environment.
- Enhanced `parseBody` function to handle request body parsing for both environments.
- Modified WebSocket handling to support Bun's WebSocket upgrade mechanism.
- Improved error handling and response structure across the server implementation.
- Added support for custom middleware in the server's request handling.
- Refactored server base functionality into `ServerBase` for better code organization.
- Updated type definitions to reflect changes in server options and listener handling.
- Added a new demo for testing the server functionality with various request types.

src/utils/is-engine.ts

@@ -2,9 +2,13 @@ export const isNode = typeof process !== 'undefined' && process.versions != null
 export const isBrowser = typeof window !== 'undefined' && typeof document !== 'undefined' && typeof document.createElement === 'function';
 // @ts-ignore
 export const isDeno = typeof Deno !== 'undefined' && typeof Deno.version === 'object' && typeof Deno.version.deno === 'string';
+// @ts-ignore
+export const isBun = typeof Bun !== 'undefined' && typeof Bun.version === 'string';
 
 export const getEngine = () => {
-  if (isNode) {
+  if (isBun) {
+    return 'bun';
+  } else if (isNode) {
     return 'node';
   } else if (isBrowser) {
     return 'browser';