feat: import highlight core only (#402)

* feat: import highlight core only

* feat: improve Hljs types

Author: HaydenOrz

src/markdownRender/extensions/index.ts

@@ -1,11 +1,14 @@
-import hljs from 'highlight.js';
+import type * as Hljs from 'highlight.js';
+import hljsCore from 'highlight.js/lib/core';
 import sql from 'highlight.js/lib/languages/sql';
 import showdown from 'showdown';
 
 import 'highlight.js/styles/default.css';
 import '../theme/vs.scss';
 import '../theme/vs-dark.scss';
 
+const hljs = hljsCore as typeof Hljs;
+
 hljs.registerLanguage('sql', sql);
 
 export default function sqlHighlightExtension(): showdown.ShowdownExtension {