Feature Request: Chain icons and ChainDropdown component

This example is from Uniswap and is very common for multi-chain and defi. I know we are Base-first and all, but I would personally have benefitted in apps prior to even just have icons for chains at my fingertips. It's annoying to find the exact brand asset and copy it into my codebase. I also have always made a `` component that automatically shows the right icon for a specific `chainId`.


Start by reviewing the existing React component library and the proposed ChainIcon and ChainDropdown components. Determine which chain icons and chainId behaviors are in scope from the issue, then identify how completion should be verified, since no files, tests, or exact supported-chain list are provided.

Written by the indexing model from the issue text.