Do not mutate request.method when checking file exists (#470)

* Do not mutate request.method with default...

...since it leads to unwanted HEAD request when the request options are specified by the user.

* Update src/file.js

The method needs to be passed to fetch ;)

Co-authored-by: Ben Zörb <ben@sommerlaune.com>

src/file.js

@@ -145,12 +145,12 @@ async function fileExists(href, options = {}) {
 
   if (isRemote(href)) {
     const {request = {}} = options;
-    request.method = request.method || 'head';
+    const method = request.method || 'head';
     try {
-      const response = await fetch(href, {...options, request});
+      const response = await fetch(href, {...options, request: {...request, method}});
       const {statusCode} = response;
 
-      if (request.method === 'head') {
+      if (method === 'head') {
         return Number.parseInt(statusCode, 10) < 400;
       }