Add credits file

credits.md

@@ -0,0 +1,20 @@
+## Credits
+
+All of the original sprites used in this project were sourced from products by Nintendo/Creatures Inc./GAME FREAK Inc.
+
+All shiny sprites were made by [@Dada78641](https://twitter.com/dada78641) except where otherwise noted. In total, 1616 shiny sprites were made:
+
+* 938 sprites were made for <i title="Pokémon X and Y">X/Y</i>,
+* +29 for the <i title="Pokémon Omega Ruby and Alpha Sapphire">OR/AS</i> update,
+* +203 for the <i title="Pokémon Ultra Sun and Ultra Moon">US/UM</i> update,
+* +446 for the <i title="Pokémon Let's Go, Pikachu! and Let's Go, Eevee!">LP/LE</i> and <i title="Pokémon Sword and Shield">SW/SH</i> update.
+
+The [alternate sizes for Pumpkaboo and Gourgeist](https://github.com/msikma/pokesprite/pull/27) were contributed by [@5310](https://github.com/5310). The [Alcremie form variations](https://twitter.com/mattgcn/status/1205639857567141889) were contributed by [@mattgcn](https://twitter.com/mattgcn).
+
+Special thanks to [@koenigderluegner](https://github.com/koenigderluegner) for his help on the <i title="Pokémon Let's Go, Pikachu! and Let's Go, Eevee!">LP/LE</i> and <i title="Pokémon Sword and Shield">SW/SH</i> update and for tagging all the new inventory sprites.
+
+The raw sprite files were originally ripped by Zhorken and Kaphotics who can be found at [Project Pokémon](http://projectpokemon.org/). Thanks to Kurt for hooking me up with their work.
+
+----
+
+Feel free to use PokéSprite in your own projects or to create derivative works. We appreciate it if you credit the project, but it's not required.

readme.md

@@ -149,3 +149,5 @@ If your project uses PokéSprite and you'd like to be added to this list, feel f
 The sprite images are © Nintendo/Creatures Inc./GAME FREAK Inc.
 
 Everything else, and the programming code, is governed by the [MIT license](http://opensource.org/licenses/MIT).
+
+See [the credits file](credits.md) for contributor details.