feat: add @robonen/fetch package - lightweight fetch wrapper with V8 optimizations

Co-authored-by: robonen <26167508+robonen@users.noreply.github.com>

core/fetch/tsdown.config.ts

@@ -0,0 +1,7 @@
+import { defineConfig } from 'tsdown';
+import { sharedConfig } from '@robonen/tsdown';
+
+export default defineConfig({
+  ...sharedConfig,
+  entry: ['src/index.ts'],
+});