update readme and cargo for version up

Author: shunsock

Cargo.lock

@@ -1,6 +1,6 @@
 [package]
 name = "tzt"
-version = "0.2.0"
+version = "0.3.0"
 edition = "2021"
 license = "MIT"
 description = "simple command-line utility that converts a given time from one timezone to another."

Cargo.toml

@@ -70,7 +70,7 @@ To install the binary, you can use the following command.
 ```bash
 sudo curl -L -o \
 	/usr/local/bin/tzt \
-	https://github.com/shunsock/timezone_translator/releases/download/v0.1.0/timezone_translator &&\
+	https://github.com/shunsock/timezone_translator/releases/download/v0.3.0/timezone_translator &&\
   sudo chmod +x /usr/local/bin/tzt
 ```