feat(notmuch): use a different workspace name

The workspace name *notmuch* is more consistent with Doom's other app
workspace names like *mu4e* and *rss*.

modules/email/notmuch/autoload.el

@@ -1,5 +1,8 @@
 ;;; email/notmuch/autoload.el -*- lexical-binding: t; -*-
 
+(defvar +notmuch-workspace-name "*notmuch*"
+  "Name of the workspace created by `=notmuch', dedicated to notmuch.")
+
 ;;;###autoload
 (defun =notmuch ()
   "Activate (or switch to) `notmuch' in its workspace."
@@ -7,7 +10,7 @@
   (condition-case-unless-debug e
       (progn
         (when (modulep! :ui workspaces)
-          (+workspace-switch "*MAIL*" t))
+          (+workspace-switch +notmuch-workspace-name t))
         (if-let* ((win (cl-find-if (lambda (it) (string-match-p "^\\*notmuch" (buffer-name (window-buffer it))))
                                    (doom-visible-windows))))
             (select-window win)