Markdown Emoji is a JS library to make any text input or a textbox enable the markdown emoji.
Add the following script to you html file.
<script src="https://github.com/nkg447/markdown-emoji/releases/download/1.0/markdown-emoji.mini.js"></script>
<script>
new MarkDownEmoji(document.getElementById("input_element")).start();
</script>
The MarkDownEmoji constructor accepts an element, on which the markdown emoji will be enabled.