Register networks in Tinkernet Rings

[arrudagates]

Register the following networks and tokens in the Rings module of Tinkernet:

• [x] Moonriver
  • MOVR
  • xcKSM
  • xcTNKR
  • general erc20 contract enum variant (Erc20([u8; 20])) that maps to the proper MultiLocation
• [x] Shiden
  • SDN
  • KSM
• [x] Karura
  • KAR
  • KSM
  • LKSM
  • tKSM