Implement tox_group_self_set_typing/tox_group_peer_get_typing/etc. for NGC

[Monsterovich]

Why not add this just like we do for individual peers?

/* Errors related to setting the local user's typing status in a group. */
typedef enum Tox_Err_Group_Set_Typing {
    TOX_ERR_GROUP_SET_TYPING_OK = 0,
    TOX_ERR_GROUP_SET_TYPING_MALLOC,
    TOX_ERR_GROUP_SET_TYPING_GROUP_NOT_FOUND,
    TOX_ERR_GROUP_SET_TYPING_NOT_CONNECTED,
} Tox_Err_Group_Set_Typing;

const char *tox_err_group_set_typing_to_string(Tox_Err_Group_Set_Typing error);

/**
 * Sets the local user's typing status in a group.
 *
 * @param tox          The Tox instance.
 * @param group_number The group number of the group.
 * @param is_typing    Whether the user is typing.
 * @param error        The error code on failure.
 *
 * @return true on success, false on failure.
 */
bool tox_group_self_set_typing(Tox *tox, uint32_t group_number, bool is_typing,
                                Tox_Err_Group_Set_Typing *error);

/* Reuses the existing group peer query error enum. */
bool tox_group_peer_get_typing(const Tox *tox, uint32_t group_number, uint32_t peer_id,
                                bool *is_typing, Tox_Err_Group_Peer_Query *error);

/* Callback fired when a peer's typing status in a group changes. */
typedef void tox_group_peer_typing_cb(Tox *tox, uint32_t group_number, uint32_t peer_id,
                                       bool is_typing, void *user_data);

void tox_callback_group_peer_typing(Tox *tox, tox_group_peer_typing_cb *callback);