/* убираем дефолтную стрелку у кнопки */
.t-btntext:after {
display: none;
}

/*Добавляем новую*/
.t-feed__button-readmore .t-btntext {
    padding-left: 0;
    padding-right: 30px;
    background-image: url(https://static.tildacdn.com/tild6231-6439-4130-a163-393830663836/Vector.svg);
    background-repeat: no-repeat;
    background-position: 95% 4px;
    text-decoration: underline;
}

.t-feed__button-readmore .t-btntext:hover {
    padding-right: 40px;
    background-image: url(https://static.tildacdn.com/tild6231-6439-4130-a163-393830663836/Vector.svg);
    background-repeat: no-repeat;
    background-position: 95% 4px;
    text-decoration: underline;
    transition-duration: 1s;
}