Single post in [dex=] Pokédex completion BBCodes

I fully support this! I wanted to something like this in my journal when I first started, and it'd be great for dexing threads or shiny/albino dex tracking in my journal too! I love the idea of being able to do something like [dex=shinydex/paldea] to show how many Paldea shiny dexes I still need to collect. Totally fine with [inventory=shinydex/paldea] format too!