feat(keybindings): add cmd+shift+p and cmd+/ keybindings from VSCode

Makes cmd+shift+p open the command palette and cmd+/ toggle comments, as
they do in VSCode.

This should ease my recent usage of Cursor/VSCode alongside Emacs, as
certain keybindings I have in Emacs cannot be setup in VSCode to work in
all contexts. Hence I've had to get used to cmd+shift+p instead of C-x
C-m, as the later does not want to play ball when a terminal is active
in VSCode.

modules/editor/siren-amx.el

@@ -12,6 +12,7 @@
   :general
   ("M-x" 'amx)
   ("C-x C-m" 'amx)
+  ("s-P" 'amx)
 
   :custom
   (amx-backend 'ido)

modules/editor/siren-smex.el

@@ -9,7 +9,7 @@
 (use-package smex
   :general
   ("C-x C-m" 'smex)
-  ("C-c C-m" 'smex)
+  ("s-P" 'smex)
   ("M-X" 'smex-major-mode-commands)
   ("C-c C-c M-x" 'execute-extended-command)