JavaScript Highlighter: batch attributed string updates to vastly improve

performance

MongoView/Synax Highlighting/JavaScriptHighlighter.swift

@@ -73,6 +73,7 @@ class JavaScriptHighlighter {
     }
     
     func highlight() {
+        attributed.beginEditing()
         let fullRange = NSRange(location: 0, length: attributed.length)
         attributed.setAttributes([
             .foregroundColor: NSColor.textColor,
@@ -83,6 +84,8 @@ class JavaScriptHighlighter {
         while let char = peek(), !expressionEnds.contains(char) {
             consumeExpression()
         }
+
+        attributed.endEditing()
     }
     
     private func emit(token: TokenType, range: NSRange) {