LGME: Adding in items.json for lab, fixing build-assets

[switch180]

Issue #, if available:

Description of changes:

• The battle-royale.zip did not have the JSON file to load items. As part of this PR we should ensure the code in the ZIP does match the lab guide, and that the ZIP correctly unpacks with the expected tree structure. On unzip, we have a folder named scripts with these contents:

  
  % tree public/assets/scripts 
  public/assets/scripts
  ├── add_inverted_index.py
  ├── add_secondary_index.py
  ├── bulk_load_table.py
  ├── create_table.py
  ├── delete_table.py
  ├── entities.py
  ├── fetch_game_and_players.py
  ├── find_games_for_user.py
  ├── find_open_games.py
  ├── find_open_games_by_map.py
  ├── items.json
  ├── join_game.py
  └── start_game.py

1 directory, 13 files

Note that the old battle-royale.tar had a separate application/ folder but we have put all files in the scripts folder.

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