Custom syntax highlighter for HTML with line numbers [on hold]

I want to have a large input text area that I can type in something. Just like in JavaScript IDEs, when I type in syntax, I want them to be highlighted as we type. In the left hand side, line number should be displayed. Because I'm using this not for programming languages, I want to add new syntax. I found some JavaScript and CSS modules like prismjs, rainbows. But I'm not sure how can I use these to a something like <textarea></textarea> where I can type.