Access to originally defined external terms

[sidvishnoi]

When Bikeshed updates anchor data from Shepherd, it lower cases lowercaseTypes, which is a good thing.
While searching for terms like sRGB, UTF-8, default toJSON steps etc, it would be nice if there was a way to access the originally defined term, and not just the lowercase ones. This would benefit fuzzy searching at https://respec.org/xref as well as bikeshed refs.

In short, consider adding a originalTerm to https://github.com/tabatkins/bikeshed/blob/b76f9052e04d33f3db06c129524d656843a82f35/bikeshed/update/updateCrossRefs.py#L335-L344

cc: @marcoscaceres

Probably related: #881, #861

[marcoscaceres]

This would be really helpful for when suggesting "how to cite" terms... right now, for example, we are suggesting "[=srgb=]" for sRGB, which is not great :( same for the others.