Improve inventory logic

[kujan]

I added some rudimentary logic to detect how many inventory pages were unlocked in the glop script, in hindsight this should be added to the Inventory class instead, because it can be used in the questing logic to avoid only using page 1.

Navigation.menu("inventory")
for btn in coords.INVENTORY_PAGE:
    res = Inputs.check_pixel_color(*btn, coords.COLOR_INVENTORY_BG)
    if not res:
        Glop.inv_pages_unlocked += 1