docs: add warning about vaults decimals

Author: Jean-Grimal

README.md

@@ -38,6 +38,9 @@ To deploy a `MorphoChainlinkOracleV2` on the Ethereum mainnet, use the `MorphoCh
 - `quoteTokenDecimals`: Decimal precision of the quote asset.
 - `salt`: A unique identifier to create deterministic addresses for deployed oracles.
 
+**Warning:** If there is an ERC4626-compliant vault for `baseVault` or `quoteVault`, the `baseTokenDecimals` or `quoteTokenDecimals` are still the decimals of the asset in the vault, and not the decimals of the Vault asset.
+E.g: for a MetaMorpho WETH vault, as `baseVault`, the `baseTokenDecimals` is 18 as WETH has 18 decimals.
+
 #### Addresses
 
 The Ethereum Mainnet address of this factory is [0x3A7bB36Ee3f3eE32A60e9f2b33c1e5f2E83ad766](https://etherscan.io/address/0x3a7bb36ee3f3ee32a60e9f2b33c1e5f2e83ad766#code).