Ci/rust toolchain

[DarthBenro008]

Description

Fixes #27

Notes to the reviewers

• Fixed a small Clippy warning and as mentioned in Rust Clippy in order to pass the build.
• Adds Cargo.toml

Checklists

All Submissions:

• [x] I've signed all my commits
• [x] I followed the contribution guidelines
• [x] I ran cargo fmt and cargo clippy before committing

New Features:

• [ ] I've added tests for the new feature
• [ ] I've added docs for the new feature
• [ ] I've updated CHANGELOG.md

[afilini]

FWIW I've confirmed locally that cargo build --features repl,electrum,esplora,compiler,compact_filters --bin bdk-cli produces the same Cargo.lock

[rajarshimaitra]

tACK.

Verified cargo.lock is same.

[notmandatory]

Sorry for the delay in merging I also had to do a rebase.