Adds just recipe for modifying cdk commit hash

[machuPikacchuBTC]

This PR addresses a comment made in #45

When you have committed your changes to the cdk fork and have a commit hash you can run just restore-deps to restore the cargo dependencies to the remote repo. Then do a search and replace across the hashpool repo to update the old commit hash to the new one. Come to think of it, that would make a great just recipe!

It's a simple "search and replace" recipe for modifying the CDK commit hash from its current value to an arbitrary rev.

Example output:

$ just update-cdk 773af52b f057cc8
Updating CDK revision from 773af52b to f057cc8...
✅ Updating ./roles/mint/Cargo.toml
✅ Updating ./roles/translator/Cargo.toml
✅ Updating ./roles/pool/Cargo.toml
✅ Updating ./protocols/v2/subprotocols/mining/Cargo.toml
Done! CDK updated from 773af52b to f057cc8

[vnprc]

Looks great! I tested this recipe in isolation and checked the diff. It is properly limited to only Cargo.toml files.

I used just update-cdk to back up one commit in the cdk repo and built it. It didn't build 😢. Then I used it again to switch back to the most recent commit. It built! \o/

When I run it while just local-cdk is active there is no conflict because it doesn't find the commit hash and is a noop.

Nice work. 🤝