Fix race condition around timeou of slow bodies

Closes remarkjs/remark-lint-no-dead-urls#53.

lib/index.js

@@ -195,6 +195,14 @@ async function deadOrAliveInternal(state, url) {
   let response
 
   try {
+    // Create a manually abortable fetch,
+    // instead of `AbortSignal.timeout(state.timeout)`.
+    // This way we only abort slow requests; not the other work.
+    const controller = new AbortController()
+    const id = setTimeout(function () {
+      controller.abort()
+    }, state.timeout)
+
     response = await fetch(url, {
       headers: {
         userAgent: state.userAgent,
@@ -207,8 +215,10 @@ async function deadOrAliveInternal(state, url) {
       },
       method: 'GET',
       redirect: 'manual',
-      signal: AbortSignal.timeout(state.timeout)
+      signal: controller.signal
     })
+
+    clearTimeout(id)
   } catch (error) {
     if (state.retries < state.maxRetries) return retry(state, url)