feat: add confirm prompt for custom keybindings

- Supports configuring a custom confirmation prompt via `config.yml` for
  custom keybindings. A new `CustomCommandPrompt.Body` field is
  used to store the immutable body text of the confirmation popup.
- Adds a sample 'confirm' prompt to the example `config.yml`.
- Updates the `Prompts` section of the documentation to include
  'confirm' prompt type and also describe which fields pertain to it
  (i.e. `initialValue`).

Closes: https://github.com/jesseduffield/lazygit/issues/1858

Signed-off-by: Michael Mead <mmead.developer@gmail.com>

pkg/gui/services/custom_commands/handler_creator.go

@@ -80,8 +80,12 @@ func (self *HandlerCreator) call(customCommand config.CustomCommand) func() erro
 				f = func() error {
 					return self.menuPromptFromCommand(resolvedPrompt, wrappedF)
 				}
+			case "confirm":
+				f = func() error {
+					return self.confirmPrompt(resolvedPrompt, g)
+				}
 			default:
-				return self.c.ErrorMsg("custom command prompt must have a type of 'input', 'menu' or 'menuFromCommand'")
+				return self.c.ErrorMsg("custom command prompt must have a type of 'input', 'menu', 'menuFromCommand', or 'confirm'")
 			}
 		}
 
@@ -112,6 +116,14 @@ func (self *HandlerCreator) menuPrompt(prompt *config.CustomCommandPrompt, wrapp
 	return self.c.Menu(types.CreateMenuOptions{Title: prompt.Title, Items: menuItems})
 }
 
+func (self *HandlerCreator) confirmPrompt(prompt *config.CustomCommandPrompt, handleConfirm func() error) error {
+	return self.c.Confirm(types.ConfirmOpts{
+		Title:         prompt.Title,
+		Prompt:        prompt.Body,
+		HandleConfirm: handleConfirm,
+	})
+}
+
 func (self *HandlerCreator) menuPromptFromCommand(prompt *config.CustomCommandPrompt, wrappedF func(string) error) error {
 	// Run and save output
 	message, err := self.git.Custom.RunWithOutput(prompt.Command)