Do not assume node_modules path

[Tronix117]

In the following file, it assumes the structure is always known and always the same.
It's not always the case, for exemple using pnpm, you have a slightly different node_modules structure

reveal-md/lib/constants.js

Line 4 in a92eb57

module.exports.highlightThemePath = path.resolve(require.resolve('highlight.js'), '..', '..', 'styles');

[webpro]

It's not pretty, but I don't see how this could be different across package managers? This is navigating within a single package.

[Tronix117]

Hello, no it's not, you go up the directories from the highlightjs package location, to get back to the root folder. When we use some other package manager like pnpm or yarn with the plug'n'play mode or non default npm mode,
you'll see the structure is quite different and this code does not work out of the box.

You can try by:

• removing node_module directory
• installing pnpm (like with npm i -g pnpm)
• running pnpm i

[webpro]

Ah yes, PnP. PR is welcome :)