While I believe it's possible that you're misinterpreting your project requirements (the rich text editor can display HTML as Erwin suggested), you can display custom HTML pages without any Java actions. Drop your HTML files into:
and then they will be accessible in your app at:
You can create folders inside the resources folder to organize your content as well. Note that this solution does not apply any security to accessing these files.
Why would you use a file from the resource folder to display help content. I would suggest using an object for this with a string attribute with unlimited length. Add the help text to the object's attribute with a rich text editor from the appstore and create a page that opens from the link that contains a rich text viewer. Doing it this way there is no need for custom java actions and the help page can be modified without re-deploying your app. Another option could be create the help in a pdf file. Upload the pdf and use the document viewer widget to display the document.
Hope this helps in finding an alternate solution.