doc: add rust-version to toml file

Author: 110CodingP

Cargo.toml

@@ -6,6 +6,7 @@ license = "MIT OR Apache-2.0"
 description = "Persistence backend for bdk using redb"
 repository = "https://github.com/110CodingP/bdk_redb"
 readme = "README.md"
+rust-version = "1.85.0"
 
 [dependencies]
 bdk_wallet = {version = "2.0.0", optional = true}