Custom Command chapter updates (#1565)

* Updates to Custom Commands chapter

* Move straggler Command-Signature info into main chapter

* Fix typos

* Add multi-parameter info

* Fixed issues from review

* Fixed typo

Author: NotTheDr01ds

.vuepress/configs/sidebar/en.ts

@@ -53,7 +53,6 @@ export const sidebarEn: SidebarConfig = {
         '/book/scripts.md',
         '/book/modules.md',
         '/book/overlays.md',
-        '/book/command_signature.md',
         '/book/testing.md',
         '/book/style_guide.md',
       ],