website: Add page for Heterogarnet

This page describes the usage of Heterogarnet and would
be helpful for users to build custom topology files and
understand the functioning of the different units within
HeteroGarnet.

Change-Id: I93541ad7ddf6f9b5748f6b3532fadf1ae1a18b2c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5-website/+/62231
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Tested-by: Bobby Bruce <bbruce@ucdavis.edu>
4 files changed