It depends on how many keywords you want to put into the package. If they're between like 9 or 15 or something, then you could think about putting it as a script filter and showing the information directly in the Alfred window itself. If you want to use the quicklook option, then just create the html file and do something like "qlmanage -p index.html" because quicklook works with html natively, although css support is minimal and there is no javascript support. For css, you do need to include it all in the document itself — no external css files.
Another option that you could do is to look into automator applications. You can create one that simply uses the "open a webpage in a hud" (or something like that) action and opens a specific html page. Then export it as an application. After that, you'd just open the application via the path (you could do this in bash with "open path/to/appname.app").
If these are all static files, then you could just put them in the workflow directory itself (cmd+click on the workflow in Alfred Preferences and select "Show in Finder"). Then just call them via the relative paths.
