node: add basic skipping

The mighty skip comes to node, putting it nearly in the range of the
compiled languages.

Even though it isn't as fast as the compiled languages, this is still
objectively fast. Unless the file is already cached in memory, you're
well into the realm of being i/o bound instead of node being the
bottleneck.

Author: rmg

Diff for: README.md

@@ -79,6 +79,7 @@ implementations compare to each other.
 | simple (Rust) | 0m1.461s | 0m1.325s | 0m0.131s |
 | skip (Rust) | 0m0.231s | 0m0.105s | 0m0.124s |
 | simple (Node) | 0m6.458s | 0m6.043s | 0m0.627s |
+| skip (Node) | 0m1.368s | 0m1.062s | 0m0.686s |
 | custom (C) | **0m0.222s** | **0m0.079s** | **0m0.141s** |
 
 By comparing the times you can see that each implementation is more or less

Diff for: main.js

@@ -37,6 +37,10 @@ function is_hex(c) {
 function scan_slice(buf) {
   let count = 0;
   for (let i = 0; i< buf.length; i++) {
+    if (count === 0 && i+20 < buf.length && !is_hex(buf[i+20])) {
+      i += 20;
+      continue;
+    }
     if (is_hex(buf[i])) {
       count++;
       continue;