Add env command (#21)

Cargo.toml

@@ -8,6 +8,7 @@ members = [
     "basename",
     "dirname",
     "echo",
+    "env",
     "wc",
 ]
 

README.md

@@ -36,7 +36,7 @@ This began as, and continues to be, a learning exercise to better understand the
 | dirname | :white_check_mark: |
 | du |  |
 | echo | :white_check_mark: |
-| env |  |
+| env | :white_check_mark: |
 | expand |  |
 | expr |  |
 | factor |  |

env/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "env"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

env/src/main.rs

@@ -0,0 +1,5 @@
+fn main() {
+    for var in std::env::vars() {
+        println!("{}={}", var.0, var.1);
+    }
+}