feat: support require.resolve for lookup, see #168

src/fs/ifs.ts

@@ -4,4 +4,5 @@ export default interface IFS {
   existsSync: (filepath: string) => boolean;
   readFileSync: (filepath: string) => string;
   resolve: (root: string, file: string, ext: string) => string;
+  fallback?: (file: string) => string | undefined;
 }

src/fs/node.ts

@@ -27,6 +27,11 @@ const fs: IFS = {
   resolve: (root: string, file: string, ext: string) => {
     if (!extname(file)) file += ext
     return resolve(root, file)
+  },
+  fallback: (file: string) => {
+    try {
+      return require.resolve(file)
+    } catch (e) {}
   }
 }