Update content-length calculation to use buffer

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@extollo/lib",
-  "version": "0.9.20",
+  "version": "0.9.21",
   "description": "The framework library that lifts up your code.",
   "main": "lib/index.js",
   "types": "lib/index.d.ts",

src/http/lifecycle/Response.ts

@@ -243,7 +243,7 @@ export class Response {
         await this.sending$.next(this)
 
         if ( !(this.body instanceof Readable) ) {
-            this.setHeader('Content-Length', String((this.body?.length ?? 0) + 2))
+            this.setHeader('Content-Length', String(Buffer.from(this.body ?? '').length))
         }
 
         this.setHeader('Date', (new Date()).toUTCString())