[Store module] Steam group

Bonus for players that are in specific steam group. To be honest I did almost nothing since I don't have any basic skills in C# and this plugin is much more copy paste from other open-source plugins such as:

• Store-NameBonus by NaathySz (everything)
• CS2-SteamGroupReward by daffyyyy (functions to fetch members from steam group and check players if they are in that specific steam group)

Config

Config will be auto generated. Default:

{
  "steamgroupid": 123456,
  "bonus_credits": 100,
  "interval_in_seconds": 100,
  "show_ad_message": true,
  "ad_message_delay_seconds": 100,
  "ad_message": "Join steam group to gain bonus credits!",
  "ConfigVersion": 1
}