refactor: use scalafmt to format code

.editorconfig

@@ -0,0 +1,12 @@
+root = true
+
+[*]
+indent_style = space
+indent_size = 2
+end_of_line = lf
+insert_final_newline = true
+
+[Makefile]
+indent_style = tab
+indent_size = 4
+

.scalafmt.conf

@@ -0,0 +1,2 @@
+version = 3.8.6
+runner.dialect = scala36

src/main/wacc/Main.scala

@@ -6,7 +6,8 @@ def main(args: Array[String]): Unit = {
   println("hello WACC!")
 
   args.headOption match {
-        case Some(expr) => parser.parse(expr) match {
+    case Some(expr) =>
+      parser.parse(expr) match {
         case Success(x)   => println(s"$expr = $x")
         case Failure(msg) => println(msg)
       }