[feat] Add "Before Dev Command" and "Before Build Command" prompts to `tauri init`

[lorenzolewis]

Reference: tauri-apps/create-tauri-app#77

Wanting to allow a user to use create-tauri-app if they have an existing project. By adding the "Before Dev Command" and "Before Build Command" prompts it will allow a more seamless experience. These two commands seem to trip new users up a bit as well, so adding it into the prompts with some explanation could help new onboarding experience.

CC @amrbashir