fix(haskell): add description for haskell, used by the explain command (#1141)

src/modules/mod.rs

@@ -113,6 +113,7 @@ pub fn description(module: &str) -> &'static str {
         "git_state" => "The current git operation, and it's progress",
         "git_status" => "Symbol representing the state of the repo",
         "golang" => "The currently installed version of Golang",
+        "haskell" => "The currently used version of Haskell",
         "hg_branch" => "The active branch of the repo in your current directory",
         "hostname" => "The system hostname",
         "java" => "The currently installed version of Java",