freadln.c: add flushing of STDOUT

c-programming/io/freadln.c

@@ -30,6 +30,10 @@ ssize_t freadln(char** output, size_t* length_out) {
 	if (output == NULL)
 		return freadln_ERROR;
 
+	// NOTE: if the file is STDIN, flush STDOUT before waiting for input to
+	// make sure a prompt is displayed
+	fflush(stdout);
+
 	freadln_length_type length = 0;
 
 	*output = malloc((length + 1) * sizeof(char));