Add comments for genesis loading method and type definitions

- Added a comment explaining the necessity to load the JSON file in a specific way in `handleGenesis`.
- Updated a comment to clarify the ID field in the `SupplyDenom` type in `schema.graphql`.
- Added a comment describing the `BlockSupply` type as a join entity between `Block` and `Supply`.

Author: jorgecuesta

schema.graphql

@@ -15,7 +15,7 @@ type EventAttribute @entity {
 }
 
 type SupplyDenom @entity {
-  # denomination indeed
+  # ID is the supply coin denomination.
   id: ID!
 }
 
@@ -134,6 +134,7 @@ type Supply @entity {
   blocks: [BlockSupply]! @derivedFrom(field: "supply")
 }
 
+# This entity is a Join between Block and Supply
 type BlockSupply @entity {
   id: ID!
   block: Block!

src/mappings/primitives.ts

@@ -44,6 +44,7 @@ import {
 } from "./utils";
 
 export async function handleGenesis(block: CosmosBlock): Promise<void> {
+  // we MUST load the JSON this way due to the sandboxed environment
   // eslint-disable-next-line @typescript-eslint/no-var-requires
   const genesis: Genesis = require("../../genesis.json");