Update MarkdStage external plugin to v4.6.3

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: d58ed1c6-561c-494a-83d1-c9e7d34e6e4c

.github/plugin/marketplace.json

@@ -1346,7 +1346,7 @@
     {
       "name": "markdstage",
       "description": "Create, edit, present, and export Markdown slides in a GitHub Copilot Canvas.",
-      "version": "4.5.1",
+      "version": "4.6.3",
       "author": {
         "name": "Kazuki Ota",
         "url": "https://github.com/runceel"
@@ -1364,8 +1364,8 @@
         "source": "github",
         "repo": "runceel/MarkdStage",
         "path": ".github/plugin/markdstage",
-        "ref": "v4.5.1",
-        "sha": "5dc37ba46d1e61422d2764e7ae89e0a2975f19fa"
+        "ref": "v4.6.3",
+        "sha": "2ee5fa20ce228a4f6aa9b105afe83ab6d2061730"
       }
     },
     {