Update manual URL.

plugin.json

@@ -8,7 +8,7 @@
   "authorEmail": "contact@vcvrack.com",
   "authorUrl": "https://vcvrack.com/",
   "pluginUrl": "https://vcvrack.com/Prototype.html",
-  "manualUrl": "https://github.com/VCVRack/VCV-Prototype/blob/master/README.md",
+  "manualUrl": "https://vcvrack.com/Prototype.html#manual",
   "sourceUrl": "https://github.com/VCVRack/VCV-Prototype",
   "donateUrl": "",
   "changelogUrl": "https://github.com/VCVRack/VCV-Prototype/blob/master/CHANGELOG.md",