Fixing typo in conversion function BigInt (#87)

Author: juanigallo

pages/en/developer/assemblyscript-api.mdx

@@ -684,7 +684,7 @@ When the type of a value is certain, it can be converted to a [built-in type](#b
 | Bytes                | JSON                 | json.fromBytes(s)            |
 | int8                 | i32                  | none                         |
 | int32                | i32                  | none                         |
-| int32                | BigInt               | Bigint.fromI32(s)            |
+| int32                | BigInt               | BigInt.fromI32(s)            |
 | uint24               | i32                  | none                         |
 | int64 - int256       | BigInt               | none                         |
 | uint32 - uint256     | BigInt               | none                         |