const addLinks = (searchPhrase, hyperlink) => {
    const document = DocumentApp.getActiveDocument();
    const body = document.getBody();
    let search = null;
    let count = 0;
    while (count < 1 && (search = body.findText(searchPhrase, search))) {
        const searchElement = search.getElement();
        const startIndex = search.getStartOffset();
        const endIndex = search.getEndOffsetInclusive();
        searchElement.asText().setLinkUrl(startIndex, endIndex, hyperlink);
        count++;
    }
    document.saveAndClose();
};

addLinks("Kiton", "https://2men.it/collections/kiton/");