Fixed empty inputs breaking the interactive repl

Also tweaked README.md and CONTRIBUTING.md

CONTRIBUTING.md

@@ -26,10 +26,10 @@ These data structures should be as independent as they can be, but there are som
 
 ```mermaid
 graph TB
-    Toy_Value ---> Toy_Stack
-    Toy_Value ---> Toy_String
-    Toy_Value ---> Toy_Table
     Toy_Bucket ---> Toy_String
+    Toy_Value ---> Toy_String
+    Toy_Value ---> Toy_Stack
+    Toy_Value ---> Toy_Table
     Toy_Array
 ```
 

README.md

@@ -23,7 +23,11 @@ This repository holds the reference implementation for Toy version 2.x, written
 # Syntax
 
 ```toy
-print 42; //print is a built-in keyword
+//print is a built-in keyword, that can handle complex expressions
+print 6 * 7;
+
+//strings can be concatenated with the .. operator
+print "Hello" .. "world!";
 
 //more examples to be added as the features are implemented
 ```

repl/main.c

@@ -186,6 +186,11 @@ int repl(const char* name) {
 			inputBuffer[--length] = '\0';
 		}
 
+		if (length == 0) {
+			printf("%s> ", name); //shows the terminal prompt
+			continue;
+		}
+
 		//end
 		if (strlen(inputBuffer) == 4 && (strncmp(inputBuffer, "exit", 4) == 0 || strncmp(inputBuffer, "quit", 4) == 0)) {
 			break;