cmd/bundle: add brew bundle edit command.

This is shorthand for `brew edit <Brewfile path>`.

cmd/bundle.rb

@@ -49,6 +49,9 @@ class BundleCmd < AbstractCommand
 
           By default, only Homebrew formula dependencies are listed.
 
+          `brew bundle edit`:
+          Edit the `Brewfile` in your editor.
+
           `brew bundle exec` <command>:
           Run an external command in an isolated build environment based on the `Brewfile` dependencies.
 
@@ -110,7 +113,7 @@ class BundleCmd < AbstractCommand
         conflicts "--all", "--no-vscode"
         conflicts "--vscode", "--no-vscode"
 
-        named_args %w[install dump cleanup check exec list]
+        named_args %w[install dump cleanup check exec list edit]
       end
 
       sig { override.void }
@@ -174,6 +177,8 @@ def run
             whalebrew:  args.whalebrew? || no_type_args,
             vscode:
           )
+        when "edit"
+          exec_editor(Bundle::Brewfile.path(global:, file:))
         when "cleanup"
           Bundle::Commands::Cleanup.run(global:, file:, force:, zap:)
         when "check"