JSFiddle - React, Tailwind, and code Playground

by the wazz

HTML

<div class="wrapper">
    <div class="panel-heading"></div>
    <h3 class="panel-title">Select Activity Stream</h3>
</div>

CSS

.wrapper {
    background-color: #ddd;
    height: 30px;
}
.panel-heading {
    height: 0;
    width: 0;
    border-bottom: 30px solid transparent;
    border-left: 30px solid blue;
    float: left;
}
h3 {
    line-height: 30px;    
}