Update index.md
Update index.md

Added banner for invite
Link to NadekoBot server
halitalf/NadekoMods,Blacnova/NadekoBot,shikhir-arora/NadekoBot,miraai/NadekoBot,powered-by-moe/MikuBot,blitz4694/NadekoBot,WoodenGlaze/NadekoBot,Midnight-Myth/Mitternacht-NEW,blitz4694/NadekoBot,PravEF/EFNadekoBot,rumlefisk/NadekoBot,Youngsie1997/NadekoBot,N1SMOxGT-R/NeoBot,gfrewqpoiu/NadekoBot,Nielk1/NadekoBot,Uleyethis/FightBot,N1SMOxGT-R/NeoBot,Taknok/NadekoBot,justinkruit/DiscordBot,justinkruit/WIABot,ShadowNoire/NadekoBot,Reiuiji/NadekoBot,Track44/Nadeko,Midnight-Myth/Mitternacht-NEW,ScarletKuro/NadekoBot,Midnight-Myth/Mitternacht-NEW,Midnight-Myth/Mitternacht-NEW,Grinjr/NadekoBot