This CL attempts to add a index.html landing page for listing
all the tools V8 has with brief descriptions within
V8's tools directory.

Screen Shots: https://imgur.com/a/NwWTI0d

Bug: v8:10664
Change-Id: I945e78381797966d6ebcd754126d26973ca9f649
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2275962Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Sathya Gunasekaran  <gsathya@chromium.org>
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Commit-Queue: Zeynep Cankara <zcankara@google.com>
Cr-Commit-Position: refs/heads/master@{#68706}