Write FX Subgraph Rewriter tutorial (#51531)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/51531
Test Plan: Imported from OSS
Reviewed By: jamesr66a
Differential Revision: D26192992
Pulled By: ansley
fbshipit-source-id: 769901b418d4580cdf8aed2451dd8ef3d8ddf0d1
