Add Viem documentation

[aefhm]

Description

Viem has changed a bit since when we opened #164. This snippet works with Viem examples.

TODO

• [x] Additional documentation
• [x] File PR for Viem chains
• [x] Simplify import conditional on https://github.com/wevm/viem/pull/1541
• [ ] Add test with Vigil.sol

[aefhm]

This is now fairly stale and provides less support #303.