Multi shells (#254)

Add multi-shells

src/commands/shells.rs

@@ -0,0 +1,18 @@
+use crate::errors::ShellError;
+use crate::object::TaggedDictBuilder;
+use crate::prelude::*;
+
+pub fn shells(args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let mut shells_out = VecDeque::new();
+    let span = args.call_info.name_span;
+
+    for shell in args.shell_manager.shells.lock().unwrap().iter() {
+        let mut dict = TaggedDictBuilder::new(Tag::unknown_origin(span));
+        dict.insert("name", shell.name());
+        dict.insert("path", shell.path());
+
+        shells_out.push_back(dict.into_tagged_value());
+    }
+
+    Ok(shells_out.to_output_stream())
+}