You can probably include html/docset inside resources bundle of your framework. Or make it available as separate download on your website.
In any case installing it to Xcode (such as your users would be able to option+click on symbols or search the, in docs) would require your users copying the docset to ~/Library/Xcode/Shared/DocSets (something like it, I'm not behing my computer so can't verify - take a look to appledoc source code to see default location, GBApplicationSettingsProvider would probably be the place).
Tom