I don't understand what you want to achieve. The custom.css can be used for the template of the LMS, I don't understand how you want to use a .js file in the learning objects.
@gihel, with forma 2 you could try to insert script tags within your html source and try to call $ as jquery is already included, but I can't say whether it would work.
As an alternative, you may consider to build a SCORM package with all the resources you need, but to do this you should learn a lot of things...
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