Synhi is a tool in one function to create own syntax themes.
That's all code you need: synhi.js.
Example:
.hl_keyword {color: blue;}
Call the function and pass element with text, regex rule to find it and class that will highlight the text.
highlight(target_element, /(keyword)/, "hl_keyword");
That result you will get:
This example does not cover the entire ini syntax; it is made to show the capabilities of the tool.
https://jsfiddle.net/ColdSpirit/6v74p8x5/
Demo backup: demo_ini.html