Refactor lexer header to define StringLiteral struct and add placeholders for ArrayLiteral, TokenString, and TypeTuple

SLS_C/include/sls/lexer.h

@@ -46,6 +46,33 @@ typedef struct {
 typedef struct {
     const char *value;
     size_t length;
-} String;
+} StringLiteral;
+
+typedef struct {
+    // TODO
+} ArrayLiteral;
+
+typedef struct {
+    // TODO
+} TokenString;
+
+typedef struct {
+    // TODO
+} TypeTuple;
+
+typedef struct {
+    TokenType type;
+    union {
+        Identifier identifier;
+        IntegerLiteral integer_literal;
+        float float_literal;
+        double double_literal;
+        StringLiteral string_literal;
+        uint8_t boolean_literal;
+        ArrayLiteral array_literal;
+        TokenString token_string;
+        TypeTuple type_tuple;
+    };
+} Token;
 
 #endif // SLS_LEXER_H