refactor: remove boilerplate parser

src/main/wacc/parser.scala

@@ -1,20 +1,8 @@
 package wacc
 
-import parsley.{Parsley, Result}
-import parsley.expr.chain
-
-import lexer.implicits.implicitSymbol
-import lexer.{integer, fully}
+import parsley.Result
 
 object parser {
   def parse(input: String): Result[String, BigInt] = parser.parse(input)
-  private val parser = fully(expr)
-
-  private val add = (x: BigInt, y: BigInt) => x + y
-  private val sub = (x: BigInt, y: BigInt) => x - y
-
-  private lazy val expr: Parsley[BigInt] =
-    chain.left1(integer | "(" ~> expr <~ ")")(
-      ("+" as add) | ("-" as sub)
-    )
+  private val parser = lexer.fully(???)
 }