PlugOS refactor and other tweaks (#631)

* Prep for in-process plug loading (e.g. for CF workers, Deno Deploy)
* Prototype of fixed in-process loading plugs
* Fix: buttons not to scroll with content
* Better positioning of modal especially on mobile
* Move query caching outside query
* Fix annoying mouse behavior when filter box appears
* Page navigator search tweaks

common/syscalls/language.ts

@@ -16,9 +16,7 @@ export function languageSyscalls(): SysCallMapping {
       }
       return parse(lang, code);
     },
-    "language.listLanguages": (
-      _ctx,
-    ): string[] => {
+    "language.listLanguages": (): string[] => {
       return Object.keys(builtinLanguages);
     },
   };