How to include libraries (CSS, JS) in WebStorm?

Question

css

Hello.
Playing around with WebStorm, PhoneGap + Onsen UI . I created the PhoneGap + Onsen UI template project, then opened it in WebStorm, but I did not receive any code completion. Tried to add JS libraries, still the same. And how to add CSS - I didn’t find it at all.
The structure of the project, circled in blue is where I would like to get code completion in the project:

Well, the second image, how it works on Onsen UI, circled in blue is what does not work (in terms of code completion).

PS
Template can be downloaded here , titled "Sliding menu".

Answer 1

Answer from JetBrains:

actually connecting libraries has nothing to do with custom HTML tags. In order for the IDE to recognize them, special support is required (as is done for AngularJS tags, for example). The easiest way to get rid of errors is to add the appropriate tags to the list of custom tags in Settings/Inspections/HTML/Unknown HTML tag. The easiest way to do this is with Alt + Enter - hover over the error, Alt + Enter, 'Add ons-sliding-menu to custom HTML tags'
After that, the tag will even appear in the compliment :) But it will not be interpreted in any special way, of course - none artificial intelligence is not to be expected here :)

Answer 2

(Removed. Misunderstood, sorry)