[vector] RFC: Javadoc for jdk.incubator.vector package

[Kharbas, Kishor]

Hi Brian,

Here is an attempt to add Javadoc for jdk.incubator.vector package - http://cr.openjdk.java.net/~kkharbas/vector-api/webrev_package_info.00
and the generated Javadoc here - http://cr.openjdk.java.net/~kkharbas/vector-api/jdk.incubator.vector/jdk/incubator/vector/package-summary.html

The api is still undergoing changes, so some parts of specification would change (e.g. fromArray()). But I think it's a good idea to start the discussion at the higher level.
I am not an expert in writing api specification, so looking forward to your feedback and guidance.

Thank you,
Kishor