Function usdToToken

usdToToken(
    client: {},
    network: EVMNetworkId,
    usdAmount: number,
    tokenSymbol: string,
    tokenDecimals: number,
): Promise<bigint>
Convert USD amount to token amount using Chainlink price feed
Parameters
- client: {}
  Viem public client
- network: EVMNetworkId
  Network identifier
- usdAmount: number
  Amount in USD (e.g., 1.00 for $1)
- tokenSymbol: string
  Token symbol (ETH, LINK, etc.)
- tokenDecimals: number
  Token decimals (18 for ETH, 18 for LINK)
Returns Promise<bigint>
Amount in token's smallest unit (wei for ETH)
Example
```
// Convert $10 USD to ETH wei
const ethWei = await usdToToken(client, 'eip155:8453', 10.0, 'ETH', 18);
console.log(`$10 = ${formatEther(ethWei)} ETH`);
```
- Defined in utils/chainlink.ts:210