Resolve "Couldn't read Hardhat config file"

[solimander]

This PR fixes an issue where Tenderly throws Couldn't read Hardhat config file when attempting to use tenderly export against newer Hardhat versions.

The underlying error is: TypeError: Do not know how to serialize a BigInt. Hardhat now uses BigInts in its config, which are not serializable, so we must convert them to strings during the JSON.stringify call.

This is likely the cause of the failure seen in #110

[samholmes]

First attempt at using Tenderly CLI to export my hardhat transactions during development and it failed because of this error. I am blocked on using Tenderly until this is fixed. I'd patch myself, but that'd require that I build my own binary (which I don't want to get into if I don't have too).

Please someone review and publish a hotfix release!

[alexanderattar]

Bumping this as it seems to be the same issue I ran up against yesterday #139
Would appreciate if the fix could be made 🙏