Built in cache doesn't seem to be working about arelle

[mrbrianevans]

I considered that the built-in cache might not be supplied with the prebuilt binary released on github, so I've manually populated my cache by copying the directory from the github repo to my local arelle cache.
Its now able to avoid download common schema files straight away from startup.
No longer an issue for me, but perhaps helpful to others to document which releases include the built-in cache files and which don't (if not already documented somewhere).

[austinmatherne-wk]

It's included in the prebuilt binary releases. The built-in cache is only active if the --offline parameter is used. This is to make sure users can load an updated version of the LRR and similar files when updates are posted.