feat: add options for NBT Short and Byte tags

[MemencioPerez]

This PR adds options for NBT short tags. I know it's not something that has common usage on Spigot or Paper servers, but I think some people who have hybrid Forge/Bukkit servers with the Pixelmon mod would like to see this feature added.

Example (uses PixelmonExtension PlaceholderAPI expansion):

items:
  'slot_1':
    material: PIXELMON_PIXELMON_SPRITE
    nbt_strings:
    - 'form:%pixelmon_party_1_form_unlocalized%'
    - 'palette:%pixelmon_party_1_palette_unlocalized%'
    nbt_short: 'ndex:%pixelmon_party_1_dex_number%'
    slot: 11
    priority: 1
    display_name: "&e(&b%pixelmon_party_1_name%&e) &7| &bNivel %pixelmon_party_1_level%"
    lore:
    - ""
    - "&7Género: &b%pixelmon_party_1_gender%"
    - "&7Habilidad: &b%pixelmon_party_1_ability%"
    - "&7Naturaleza: &b%pixelmon_party_1_nature%"
    - "&7Tamaño: &b%pixelmon_party_1_growth%"
    - "&7Forma: &b%pixelmon_party_1_form%"
    - "&7Paleta: &b%pixelmon_party_1_palette%"

[MemencioPerez]

I have also added options for NBT byte tags.