Add assignment 4

src/assignments/assignment04/parser.rs

@@ -0,0 +1,19 @@
+//! Parser.
+
+use super::syntax::*;
+use anyhow::Result;
+
+#[allow(missing_docs)]
+#[allow(missing_debug_implementations)]
+mod inner {
+    use pest_derive::*;
+
+    #[derive(Parser)]
+    #[grammar = "assignments/assignment04/syntax.pest"]
+    pub(crate) struct SyntaxParser;
+}
+
+/// Parses command.
+pub fn parse_command(line: &str) -> Result<Command> {
+    todo!("fill here")
+}