docs(configuration): add output.environment.document (#7374)

Author: snitin315

src/content/configuration/output.mdx

@@ -488,6 +488,8 @@ module.exports = {
       const: true,
       // The environment supports destructuring ('{ a, b } = obj').
       destructuring: true,
+      // The environment supports 'document' variable.
+      document: true,
       // The environment supports an async import() function to import EcmaScript modules.
       dynamicImport: false,
       // The environment supports an async import() when creating a worker, only for web targets at the moment.