How to add to regex for keyword detection (TODO|FIXME) to capture additional keywords

RStudio includes two keywords that trigger the .ace_comment.ace_keyword.ace_operator style definition, FIXME and TODO.

The definitions for these keywords, and all others that have syntax highlighting applied, are in the source (rstudio/r_highlight_rules.js at 295d51d5adc623a7c44d3647bab0dd39926758e1 · rstudio/rstudio · GitHub).

However it appears that the regex definitions are no longer exposed after compiling.

Short of editing that file and compiling on my own, is there any way to add regex definitions for .ace_comment.ace_keyword.ace_operator, or even to create new keyword definitions that map to new .ace theme css?