So far, the list of resources is a collection of PDFs I've downloaded plus a script to download the latest version of every relevant specification. (Although it does seem that Intel likes breaking its links to the latest ISA PDF every now and then). I don't have a great solution for things that are essentially web-only pages, which is how the Itanium ABI is handled (and unlike C, C++ makes it hard to find the relevant working draft copies, instead preferring to use the HTML-based
https://eel.is/c++draft for that).
I probably will make it publicly available eventually, it just hasn't been a priority for me.