Document API versions (#643)

website/pages/en/developing/graph-ts/api.mdx

@@ -29,6 +29,8 @@ The `apiVersion` in the subgraph manifest specifies the mapping API version whic
 
 | Version | Release notes |
 | :-: | --- |
+| 0.0.9 | Adds new host function `eth_get_balance` |
+| 0.0.8 | Adds validation for existence of fields in the schema when saving an entity. |
 | 0.0.7 | Added `TransactionReceipt` and `Log` classes to the Ethereum types<br />Added `receipt` field to the Ethereum Event object |
 | 0.0.6 | Added `nonce` field to the Ethereum Transaction object<br />Added `baseFeePerGas` to the Ethereum Block object |
 | 0.0.5 | AssemblyScript upgraded to version 0.19.10 (this includes breaking changes, please see the [`Migration Guide`](/release-notes/assemblyscript-migration-guide))<br />`ethereum.transaction.gasUsed` renamed to `ethereum.transaction.gasLimit` |