Link to website overview slides in docs/README.md. (#14400)

I presented these slides at an internal team meeting and may repeat the
presentation for the broader community if there is interest and a time
slot.

The slides should be world-readable (except where `docs.google.com` is
blocked). I tried exporting to .pdf but don't want to commit a 1.3MB
file to the repo (lots of screenshots, even with good compression).

docs/README.md

diff --git a/docs/README.md b/docs/README.md
index 43bf803..7174d47 100644
--- a/docs/README.md
+++ b/docs/README.md
@@ -22,3 +22,7 @@
 
 Developer documentation _can_ compromise on each of these points. Pages may
 also be promoted to website/ after some refinement.
+
+For more details on how this is set up, see
+
+* [IREE Website Overview - July 10, 2023](https://docs.google.com/presentation/d/116TyW_aCsPXmmjRYI2tRqpOwDaGNoV8LDC_j9hsMrDk/edit?usp=sharing)