feat: some enhancements

[lawvs]

• Add a group preset

export const DEFAULT_GROUP = [
  "Social",
  "Entertainment",
  "Read Material",
  "Education",
  "Productivity",
  "Utilities",
];

• Add a loading indicator

• Update the type of getStorage API, it may return a undefined
• Remove incorrect usage about the chrome.runtime.sendMessage
• Save the API key to storage when blurring instead when clicking the group button.
• Add a tip for get the API key

• Remove the background of the icon. (I use the Photopea)