fix: use oxc instead of esbuild when Rolldown is detected

[AlexDemzz]

Fixes #142

Vite 8 dropped esbuild in favor of oxc for JS transforms. The plugin was still setting esbuild.banner unconditionally, which produces this warning:

`esbuild` option was specified by "vite-plugin-node-polyfills" plugin.
This option is deprecated, please use `oxc` instead

The fix uses the existing isRolldownVite check to pick between oxc.jsxInject and esbuild.banner for dev banner injection, same pattern already used for optimizeDeps.rolldownOptions vs esbuildOptions.

-        esbuild: {
-          banner: isDev ? globalShimsBanner : undefined,
-        },
+        ...(isRolldownVite
+          ? { oxc: { jsxInject: isDev ? globalShimsBanner : undefined } }
+          : { esbuild: { banner: isDev ? globalShimsBanner : undefined } }
+        ),

Also adds ^8.0.0 to peerDependencies.