How does one extend built-in parsers/tokenizers?

For example:

const linksidx = md.inline.ruler.__find__('links')
const oldlinks = md.inline.ruler.__rules__[linksidx].fn
const links = function (state, startLine, endLine, silent) {
    console.log(state)
    const ret = oldlinks(state, silent)
    if (!ret) return false

    console.log(state) /* This just returns the cumulative
        state object, without the ability to modify the
        particular link instance that was just captured. */
    return true
}
md.inline.ruler.at("links", links)

But to add custom attributes, one would need to import all the dependencies in lib/rules_inline/links.js and basically copy/paste the function, but the lib dir does not come with the node package. Also, this API seems to be a roundabout way to override or extend parser rules. Is there a better way?

Example case: add dimensions to images with a custom extension:

[alt text](https://example.com/image.jpg)[500x300]

I guess I will have to add it to the ALT text like:

[@500x300,alt text here](https://example.com/image.jpg)

but this use case could apply to any custom token such as a heading, URL, even a table with attributes, etc.