feat(token): add String() method to token Type

Add String() method to the token Type that returns the human-readable name
of the token (e.g., "LBRACE" for '{'), with fallback to numeric value for
unknown types. Also add typeNames map for token type name lookups.

macro/interpreter/token/token.go

@@ -1,8 +1,20 @@
 package token
 
+import "strconv"
+
 // Type is a specific type of int which describes the symbols.
 type Type int
 
+// String returns the name of the token type, e.g. "LBRACE" for the '{' symbol.
+// It returns the numeric value of an unknown type as it is.
+func (t Type) String() string {
+	if name, ok := typeNames[t]; ok {
+		return name
+	}
+
+	return strconv.Itoa(int(t))
+}
+
 // Token describes the letter(s) or symbol, is a result of the lexer.
 type Token struct {
 	Type    Type
@@ -37,6 +49,20 @@ const (
 	INT // 42
 )
 
+var typeNames = map[Type]string{
+	EOF:     "EOF",
+	ILLEGAL: "ILLEGAL",
+	LBRACE:  "LBRACE",
+	RBRACE:  "RBRACE",
+	COLON:   "COLON",
+	LPAREN:  "LPAREN",
+	RPAREN:  "RPAREN",
+	COMMA:   "COMMA",
+	IDENT:   "IDENT",
+	ELSE:    "ELSE",
+	INT:     "INT",
+}
+
 var keywords = map[string]Type{
 	"else": ELSE,
 }