To make a button using CSS:

Put this inline in the article, updating the words and link as needed:

<p style="text-align: center;"><a style="text-decoration: none;" href="https://puestadelsolpta.org/Packet/YOUR-PACKET" target="_blank" rel="noopener"><button class="button-29"><strong>YOUR-WORDS</strong></button></a></p>

2. Put this at the end of the article html:

<style>
.button-29 {
  align-items: center;
  appearance: none;
  background-image: radial-gradient(100% 100% at 100% 0, #ffee00 0, #ffe600 100%);
  border: 0;
  border-radius: 6px;
  box-shadow: rgba(45, 35, 66, .4) 0 2px 4px,rgba(45, 35, 66, .3) 0 7px 13px -3px,rgba(58, 65, 111, .5) 0 -3px 0 inset;
  box-sizing: border-box;
  color: #0088dc;
  cursor: pointer;
  display: inline-flex;
  height: 48px;
  justify-content: center;
  line-height: 1;
  list-style: none;
  overflow: hidden;
  padding: 32px;
  position: relative;
  text-align: left;
  text-decoration: none;
  transition: box-shadow .15s,transform .15s;
  user-select: none;
  -webkit-user-select: none;
  touch-action: manipulation;
  white-space: nowrap;
  will-change: box-shadow,transform;
  font-size: 18px;
}
</style>

To generate links to add an event to Google/Outlook/Yahoo/etc calendar

https://www.labnol.org/calendar/