near-api (Rust) 0.8.0

Added

• Add NEP-413 message verification (#98)
• [breaking] signer interface improvement (#89)

Other

• clean up comments in utils.rs
• [breaking] simplify and remove PublicKeyProvider to improve code clarity (#95)
• restricted usage of unwrap and expects, removed some unwraps in signing (#96)
• migrated examples and tests to TestResult from unwraps
• [breaking] defer errors for contract interaction (#93)