fix(config): support npm modules for customFetch

Author: ardatan

.changeset/thick-shoes-admire.md

@@ -0,0 +1,5 @@
+---
+'@graphql-mesh/config': patch
+---
+
+Handle customFetch paths correctly

packages/config/src/utils.ts

@@ -134,9 +134,7 @@ export async function resolveCustomFetch({
     additionalPrefixes: additionalPackagePrefixes,
   });
 
-  const processedModuleName = path.isAbsolute(moduleName)
-    ? moduleName
-    : path.join('..', moduleName);
+  const processedModuleName = moduleName.startsWith('.') ? path.join('..', moduleName) : moduleName;
   importCode += `import fetchFn from ${JSON.stringify(processedModuleName)};\n`;
 
   return {