The wavedrom project : https://wavedrom.com/
Which allowed user to use text to describe waveform and render the signals for you.
I have no idea if anyone success to integrate wavedrom with Gitea?
You are looking for what is called “external renderers” in the Gitea terminology. See the documentation.
It looks like this person may have had success on this GitHub issue, perhaps you can try the solution they posted or contact them? They did not use external renderer functionality but you may be able to adapt it.