Literate coffeescript

[rmarscher]

Hi. Thanks for this extension. I have a legacy project written with literate coffeescript. I added detecting the .litcoffee extension and passing that option to the lint method. 835a6fa

I had trouble rebuilding the extension, so I reapplied the code on top of the current lsp-sample.

I also added a npm script to package the extension into a vsix file. I was able to install that, so no rush on accepting this pull request. Or feel free to close it if you aren't maintaining this project.

If anyone else wants to use this version before it is merged, you can clone rmarscher/coffeelinter, switch to the literate-coffeescript branch and then run

npm i
npm run compile
npm run package

And then you can install the output coffeelinter-1.5.0.vsix file in VSCode.

Fixes #10