Automate validation of the item database via GitHub Actions

[rdw-software]

Source: Discord

Hi, when I run /rarity validate on a database I have been using for a long time, I get some errors, how could I solve these?

There's /rarity validate to check all items for certain schema violations. But I guess this isn't as useful as checking for them automatically, as is evident by the number of items that are invalid. Every once in a while, someone asks about these perceived "errors" so perhaps the feature should just be removed from the addon itself? Or at least, it should only check Custom items and mention as much.