feat(cli): add --all option to run test command

challenges/camel-case/solutions/c/function/character.c

@@ -9,7 +9,7 @@ void character_append(char* string, char character) {
   string[length + 1] = '\0';
 }
 
-const char character_to_upper(const char character) {
+char character_to_upper(char character) {
   char ascii_a = 'a';
   char ascii_A = 'A';
   char ascii_z = 'z';

challenges/camel-case/solutions/c/function/character.h

@@ -14,8 +14,8 @@ void character_append(char* string, char character);
  * @brief Converts the character to uppercase.
  *
  * @param character
- * @return const char
+ * @return char
  */
-const char character_to_upper(const char character);
+char character_to_upper(char character);
 
 #endif