super minor fix: misprint in comment in line 21 (doesn't affect anything)

src/environment.ts

@@ -18,7 +18,7 @@ function isDefined<T>(x: string, env: Environment<T>): boolean {
 }
 
 function declare<T>(x: string, v: T, env: Environment<T>): void {
-  // 1. Add a variable represented by the parameter `x` into the environment represented by the parameters `env`.
+  // 1. Add a variable represented by the parameter `x` into the environment represented by the parameter `env`.
   // TODO: YOUR CODE HERE // Hint: You can find which methods to use at: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map
 }