add Mammoth Token

[mmtchain1]

Hello Metamask team. This PR is to register MMT auto-detected and auto-displayed on Metamask

Basic information about the project: Mammoth is a project to build an integrated infrastructure based on ecosystem resources and will gradually open to the blockchain industry.

Official Project Website: https://www.mmtchain.io/ Whitepaper: https://www.mmtchain.io/whitepaper/mammoth_whitepaper_en.pdf

Our social community: Facebook: https://www.facebook.com/Mammoth-111185404749870 Twitter: https://twitter.com/mmtchain Linkedin: https://www.linkedin.com/company/mammoth-official Discord: https://discord.com/channels/917956326045392997 Telegram Channel: https://t.me/mammothofficial Reddit: https://www.reddit.com/r/mammoth_official Medium: https://medium.com/@mmtchain