feat: default-tab in group widget

[ralphocdol]

- type: group
  default-tab: 2 # <-- making tab 2 the default
  define1: &shared-properties
      allow-potentially-dangerous-html: true
      cache: 1s
  widgets:
    - type: extension
      title: Yesterday
      url: ${URL1}
      <<: *shared-properties
    - type: extension
      title: Sonarr Now
      url: ${URL2}
      <<: *shared-properties
    - type: extension
      title: Tomorrow
      url: ${URL3}
      <<: *shared-properties