Remove ignoreBOM

Apparently the ignoreBOM option actually means "include the BOM". I've
added a test for this in my own repository, and will also be submitting
a pull request to MDN to clarify this in their documentation.

public/scripts/sse-stream.js

@@ -3,7 +3,7 @@
  */
 class EventSourceStream {
     constructor() {
-        const decoder = new TextDecoderStream('utf-8', { ignoreBOM: true });
+        const decoder = new TextDecoderStream('utf-8');
 
         let streamBuffer = '';