Reduce StreamParser chunk size

FIX: Make the stream parser user 4 times smaller chunks to reduce the amount of re-parsed
code on changes.

See https://discuss.codemirror.net/t/old-language-mode-used-in-codemirror-v6-triggers-full-re-parse-of-the-entire-document/9384

Author: marijnh

src/stream-parser.ts

@@ -181,7 +181,7 @@ function findStartInFragments<State>(lang: StreamLanguage<State>, fragments: rea
 }
 
 const enum C {
-  ChunkSize = 2048,
+  ChunkSize = 512,
   MaxDistanceBeforeViewport = 1e5,
   MaxIndentScanDist = 1e4,
   MaxLineLength = 1e4