Add a basic CONTRIBUTING.md
Add a basic CONTRIBUTING.md

Closes #2419

kuroscafe/Paradox,DesoGit/Tsunami_PS,panpawn/Pokemon-Showdown,ZestOfLife/FestiveLife,Guernouille/Pokemon-Showdown,urkerab/Pokemon-Showdown,KewlStatics/Alliance,arkanox/MistShowdown,Lord-Haji/SpacialGaze,AustinXII/Pokemon-Showdown,PS-Spectral/Spectral,xfix/Pokemon-Showdown,cadaeic/Pokemon-Showdown,Hidden-Mia/Roleplay-PS,QuiteQuiet/Pokemon-Showdown,Lord-Haji/SpacialGaze,xfix/Pokemon-Showdown,Enigami/Pokemon-Showdown,jumbowhales/Pokemon-Showdown,DesoGit/TsunamiPS,Irraquated/Pokemon-Showdown,Lord-Haji/SpacialGaze,sirDonovan/Pokemon-Showdown,KewlStatics/Showdown-Template,kuroscafe/Showdown-Boilerplate,Alpha-Devs/Alpha-Server,Git-Worm/City-PS,SkyeTheFemaleSylveon/Pokemon-Showdown,DesoGit/TsunamiPS,Pikachuun/Pokemon-Showdown,zek7rom/SpacialGaze,Pikachuun/Pokemon-Showdown,Alpha-Devs/OmegaRuby-Server,Bryan-0/Pokemon-Showdown,AustinXII/Pokemon-Showdown,Wando94/Spite,Enigami/Pokemon-Showdown,Bryan-0/Pokemon-Showdown,kuroscafe/Paradox,AnaRitaTorres/Pokemon-Showdown,QuiteQuiet/Pokemon-Showdown,xfix/Pokemon-Showdown,PS-Spectral/Spectral,Vacate/Pokemon-Showdown,DesoGit/Tsunami_PS,KewlStatics/Pokeindia-Codes,Sora-League/Sora,QuiteQuiet/Pokemon-Showdown,Flareninja/Showdown-Boilerplate,danpantry/Pokemon-Showdown,zek7rom/SpacialGaze,jumbowhales/Pokemon-Showdown,Elveman/RPCShowdownServer,aakashrajput/Pokemon-Showdown,AnaRitaTorres/Pokemon-Showdown,Zarel/Pokemon-Showdown,Vacate/Pokemon-Showdown,CreaturePhil/Showdown-Boilerplate,Flareninja/Showdown-Boilerplate,Irraquated/Pokemon-Showdown,Sora-League/Sora,danpantry/Pokemon-Showdown,HoeenCoder/SpacialGaze,AWailOfATail/Pokemon-Showdown,AWailOfATail/Pokemon-Showdown,Volcos/SpacialGaze,DesoGit/Tsunami_PS,Sora-League/Sora,ShowdownHelper/Saffron,Mystifi/Exiled,Irraquated/Pokemon-Showdown,DarkSuicune/Pokemon-Showdown,SolarisFox/Pokemon-Showdown,svivian/Pokemon-Showdown,KewlStatics/Shit,aakashrajput/Pokemon-Showdown,panpawn/Gold-Server,Hidden-Mia/Roleplay-PS,aakashrajput/Pokemon-Showdown,ZestOfLife/PSserver,azum4roll/Pokemon-Showdown,CharizardtheFireMage/Showdown-Boilerplate,panpawn/Gold-Server,kotarou3/Krister-Pokemon-Showdown,EienSeiryuu/Pokemon-Showdown,svivian/Pokemon-Showdown,svivian/Pokemon-Showdown,KewlStatics/Pokeindia-Codes,xCrystal/Pokemon-Showdown,Mystifi/Exiled,SkyeTheFemaleSylveon/Pokemon-Showdown,SolarisFox/Pokemon-Showdown,HoeenCoder/SpacialGaze,arkanox/MistShowdown,azum4roll/Pokemon-Showdown,Volcos/SpacialGaze,kotarou3/Krister-Pokemon-Showdown,EienSeiryuu/Pokemon-Showdown,Guernouille/Pokemon-Showdown,PS-Spectral/Spectral,Lauc1an/Perulink-Showdown,Zarel/Pokemon-Showdown,ShowdownHelper/Saffron,urkerab/Pokemon-Showdown,TbirdClanWish/Pokemon-Showdown,ZestOfLife/PSserver,Git-Worm/City-PS,xfix/Pokemon-Showdown,TheFenderStory/Pokemon-Showdown,Kokonoe-san/Glacia-PS,Enigami/Pokemon-Showdown,ZestOfLife/FestiveLife,Mystifi/Exiled,panpawn/Pokemon-Showdown,svivian/Pokemon-Showdown,kuroscafe/Showdown-Boilerplate,Lauc1an/Perulink-Showdown,cadaeic/Pokemon-Showdown,Enigami/Pokemon-Showdown,KewlStatics/Shit,ShowdownHelper/Saffron,xCrystal/Pokemon-Showdown,CreaturePhil/Showdown-Boilerplate,sirDonovan/Pokemon-Showdown,Wando94/Spite,CharizardtheFireMage/Showdown-Boilerplate,HoeenCoder/SpacialGaze,KewlStatics/Showdown-Template,Pikachuun/Pokemon-Showdown-SMCMDM,xCrystal/Pokemon-Showdown,jd4564/Pokemon-Showdown,BlazingAura/Showdown-Boilerplate,AWailOfATail/Pokemon-Showdown,svivian/Pokemon-Showdown,xfix/Pokemon-Showdown,KewlStatics/Alliance,Elveman/RPCShowdownServer,urkerab/Pokemon-Showdown,Pikachuun/Pokemon-Showdown-SMCMDM,Zarel/Pokemon-Showdown,HoeenCoder/SpacialGaze,jumbowhales/Pokemon-Showdown,CreaturePhil/Showdown-Boilerplate,AustinXII/Pokemon-Showdown,panpawn/Gold-Server,Alpha-Devs/OmegaRuby-Server,DarkSuicune/Pokemon-Showdown,jd4564/Pokemon-Showdown,BlazingAura/Showdown-Boilerplate,TheFenderStory/Pokemon-Showdown,TbirdClanWish/Pokemon-Showdown,sirDonovan/Pokemon-Showdown,Kokonoe-san/Glacia-PS,Alpha-Devs/Alpha-Server