Using On-screen keyboard on a web application

I am building a web based image labelling tool using Django on backend and HTML/CSS/JavaScript on the front end. The user draws a bounding box on some part of image and a box appears in which the user has to enter the label of that particular part selected in bounding box. I need the user to enter the label in ancient-greek. So I would need an on screen keyboard on my web page. Can you suggest some possible ways to achieve this?