netbeans - What is format of customs.json configuratin file? -

for php project uses custom html tags template part of framework define netbeans customs.json file, can contain these new tags. empty file in nbproject directory called customs.json looks 1 below. there descrition of can define , how in file? (e.g. definition tag can inside of tag ... tr must inside of table tag ... custom tags ...)

customs.json  {     "attributes": {},     "elements": {} } 

afaik there no documentation, easy way add definitions use custom tag/custom attribute in html file, netbeans mark error or warning bulb icon on left of line "error". click on bulb icon , ide offer define custom element, custom attribute, custom attribute on specific element etc. these action add definitions customs.json file. once this, show in code completion common tags/attributes.