fix: missing pdfjs in electron

resources/electron.html

@@ -51,6 +51,8 @@ const portal = new MagicPortal(worker);
 <script defer src="./js/highlight.min.js"></script>
 <script defer src="./js/interact.min.js"></script>
 <script defer src="./js/marked.min.js"></script>
+<script defer type="module" src="./js/pdfjs/pdf.mjs"></script>
+<script defer type="module" src="./js/pdf_viewer3.mjs"></script>
 <script defer src="./js/html2canvas.min.js"></script>
 <script defer src="./js/lsplugin.core.js"></script>
 <script defer src="./js/react.production.min.js"></script>