Include missing classes as super class of Selector

[csarven]

https://www.w3.org/TR/annotation-vocab/#selector should include the following as part super class of:

• https://www.w3.org/TR/annotation-vocab/#cssselector
• https://www.w3.org/TR/annotation-vocab/#rangeselector
• https://www.w3.org/TR/annotation-vocab/#xpathselector

[BigBlueHat]

@iherman how do we handle errata for things like this? @csarven is indeed correct (afaict) that we missed those in that list...

[iherman]

@BigBlueHat @csarven see: https://www.w3.org/annotation/errata/

The community group manages errata, b.t.w.

Cc: @azaroth42 @tcole3