fix: ghpage 404

Author: xiaohuoni

plugin.ts

@@ -0,0 +1,18 @@
+import { copyFileSync, existsSync } from 'fs';
+import { join } from 'path';
+import { IApi } from 'umi';
+
+export default (api: IApi) => {
+  api.onBuildComplete(({ err }) => {
+    //@ts-ignore
+    if (!err && !existsSync(join(api.paths.absOutputPath!, '404.html'))) {
+      // 如果没有 404 则复制一下 index
+      setTimeout(() => {
+        copyFileSync(
+          join(api.paths.absOutputPath!, 'index.html'),
+          join(api.paths.absOutputPath!, '404.html'),
+        );
+      }, 500);
+    }
+  });
+};