update to ecmel/vscode-html-css version 2

[shadowwa]

Hi,

I wanted to add the glob functionnality to be able to use something like "html-css-support.styleSheets": ["src/**/*.css"] but finally ended up updating the whole code to match the current ecmel/vscode-html-css one.

I've also modified the detail/document of the completion items to show from which file the selector come from and the css rules applied to this selector.

I'm not used to coc.nvim api and not sure I've choose the best solution when modifying the code, for example, int src/extension.ts, I had to replace

window.activeTextEditor

by

workspace.getDocument(event.bufnr).textDocument

maybe there is a simpler replacement.

The one thing I wasn't able to adapt was the range in Provider.getCompletionItems()

[yaegassy]

@shadowwa Hi, sorry for the delayed response.

Thank you for the amazing Pull Request.

It seems that the changes for v2 will significantly alter the code structure, so it might be better to create a new coc extension instead.