The FML XSD is located here.
Your favorite IDE probably supports XSD schema's for .fml files. You need to specify the following:
<faqs xmlns="http://maven.apache.org/FML/1.0.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/FML/1.0.1 https://maven.apache.org/xsd/fml-1.0.1.xsd" title="..."> ... </faqs>