build: add Node.js main file

[Kikobeats]

Hello,

In a previous PR (#114) the main field at package.json was removed because it was causing not useful.

This PR adds the field again but rather than pointing to a filesystem folder, it's returning the absolute path where the themes are living:

require('prism-themes')
// {
//  folderPath: '/Users/kikobeats/Projects/microlink/browserless/packages/screenshot/node_modules/prism-themes/themes'
// }

This is actually useful because for some bundle workflow you need the reference of the folder to copy or load the themes.

In this way, it prevents copy the whole folder, but you still have a reference to the folder path in case you need it.

[RunDevelopment]

Why do we need to export this path? Couldn't somebody that needs the path just do require.resolve('prism-themes/themes')? It's not like we plan to rename the themes folder anytime soon (since that would be a breaking change).

[Kikobeats]

@RunDevelopment that was my initial assumption and it's failing:

https://github.com/microlinkhq/browserless/blob/master/packages/screenshot/src/pretty/theme.js#L9

The assumption is wrong since the folder is going to live depending on where npm install decides to place the folder, meaning that if the project has other dependencies using prism-themes it will be placed in a place where both dependencies can find it, making the path unpredictable.

The solution is to use "main" on package.json to point to the dependency path, and because the dependency path is calculated using __dirname, you always will have the absolute path!

[RunDevelopment]

@Kikobeats Not path.resolve but require.resolve.

[Kikobeats]

@RunDevelopment require.resolve can't find the module since the package doesn't have the "main" field

[RunDevelopment]

require wants to find .js files, right... my bad. A main module is necessary in that case.

[Kikobeats]

fixed lint issues!

[Kikobeats]

added missing semicolon

[Kikobeats]

I understand although literally I just added 5 lines of javascript to make possible use it like the rest of npm dependencies

[Kikobeats]

@RunDevelopment any status of this? really want to use the library 😭

[RunDevelopment]

Sorry for the delay @Kikobeats. Let's merge this.

[Kikobeats]

@RunDevelopment thanks a lot! can you please release a new version?

[RunDevelopment]

Just published a new version @Kikobeats.