Markdown highlighting throws error

[idleberg]

Consider the following demo code:

const markdown = `
# Demo

Markdown supports *italic* and **bold** text among other things
`.trim();

console.log(chromafi(markdown, {lang: 'markdown'}));

This will produce the following error:

~/Demo/node_modules/chromafi/index.js:74
			return opts.colors[color](childText)
			                         ^

TypeError: opts.colors[color] is not a function
    at filter (~/Demo/node_modules/chromafi/index.js:74:29)
    at ~/Demo/node_modules/chromafi/index.js:71:48
    at Array.map (<anonymous>)
    at filter (~/Demo/node_modules/chromafi/index.js:71:31)
    at ~/Demo/node_modules/chromafi/index.js:146:16
    at Array.forEach (<anonymous>)
    at syntaxHlStr (~/Demo/node_modules/chromafi/index.js:143:8)
    at chromafi (~/Demo/node_modules/chromafi/index.js:387:11)
    at Object.<anonymous> (~/Demo/demo.js:9:13)
    at Module._compile (internal/modules/cjs/loader.js:759:30)

This seems to be specific to Markdown since {lang: 'html'} works just fine.

Node v12.0.0
macOS 10.14.6 (18G103)