docs: document import defer syntax (2.8)

runtime/fundamentals/modules.md

@@ -108,6 +108,30 @@ Uint8Array(12) [
 // ]
 ```
 
+## Deferred module evaluation
+
+Starting in Deno 2.8, the
+[TC39 Deferred Module Evaluation proposal](https://github.com/tc39/proposal-defer-import-eval)
+is supported. The `import defer` syntax loads a module — including its
+dependencies — but does **not** execute its top-level code until you first read
+a property from the namespace:
+
+```ts title="main.ts"
+import defer * as expensive from "./expensive.ts";
+
+console.log("startup is fast — expensive.ts has not run yet");
+
+// Touching any property triggers synchronous evaluation
+console.log(expensive.value);
+```
+
+Use it to defer the cost of modules that are only needed conditionally — for
+example, error-path code in a CLI tool or feature flags whose implementation is
+heavy to initialize.
+
+The proposal is still at TC39 Stage 3, so the syntax is considered experimental
+and may change. Standard `import` remains the right default.
+
 ## WebAssembly modules
 
 Deno supports importing Wasm modules directly: