chore(cargo): Bump version to 0.3.0

Version bump to the next minor release to express that
support for older rust versions was dropped (<1.74)

Author: jontze

Cargo.toml

@@ -2,7 +2,7 @@
 name = "tankerkoenig"
 author = "Jontze <dev@jontze.com>"
 description = "API wrapper for the tankerkoenig api"
-version = "0.2.0"
+version = "0.3.0"
 edition = "2021"
 rust-version = "1.75.0"
 license = "MIT"