created TokenMetadata model

frontend/models/TokenMetadata.ts

@@ -0,0 +1,17 @@
+export default interface TokenMetada { 
+    title: string, // ex. "Arch Nemesis: Mail Carrier" or "Parcel #5055"
+    description: string, // free-form description
+    media: string, // URL to associated media, preferably to decentralized, content-addressed storage
+    //media_hash: Base64VecU8, // Base64-encoded sha256 hash of content referenced by the `media` field. Required if `media` is included.
+    copies: number, //u64 // number of copies of this set of metadata in existence when token was minted.
+    issued_at: string, // ISO 8601 datetime when token was issued or minted
+    price: string, // is the price in yoctos
+    creator: string, // is the creator
+    on_sale: boolean, // sale status
+    expires_at: string, // ISO 8601 datetime when token expires
+    starts_at: string, // ISO 8601 datetime when token starts being valid
+    updated_at: string, // ISO 8601 datetime when token was last updated
+    extra: string, // anything extra the NFT wants to store on-chain. Can be stringified JSON.
+    reference: string, // URL to an off-chain JSON file with more info.
+   // reference_hash: <Base64VecU8>, // Base64-encoded sha256 hash of JSON from reference field. Required if `reference` is included.
+}