only allow lower case hex character for jump locations so labels like FINISH WORK

src/asm.pest

@@ -18,11 +18,11 @@ jump_instruction = {"JMP"}
 arg_instruction = {"LDA" | "ADD" | "SUB"}
 no_arg_instruction = { "NOP" }
 
-jump_argument = { jump_location | label}
+jump_argument = { jump_location | label }
 argument = { memory_location | digit_literal }
 memory_location = { "(" ~ ASCII_HEX_DIGIT ~")" }
 digit_literal = {"#" ~ ASCII_HEX_DIGIT}
-jump_location = { ASCII_HEX_DIGIT }
+jump_location = { '0'..'9' | 'a'..'f' }
 
 label = { ASCII_ALPHA_UPPER+ }