Need to download "pagedown" manually

[AzzieDev]

Since it's hosted on Google Code, which is now in a frozen archived state, download it from there and extract to "thirdparty" directory, and make sure the directory you just extracted is named "pagedown".

https://code.google.com/archive/p/pagedown/source/default/source

There may be newer forks or releases of pagedown that are maintained, but I don't know which would be supported.