As other folders are blocked in the module. You have to add the folder where the css/js is stored to the static resources in manifest (pom.xml) of the module like (e.g. the additional folder is vendor):
Now the css file will be available. Now you can use the addTemplate tag. NOTE: the addTemplate tag base the css folder!!
So you have to add something like:
<template:addResources type="css" resources="../vendor/myVendor.css" />