README.md: add example URLs

Example URLs for https://storage.googleapis.com/go-vulndb are added to
the README.

Change-Id: I933d3896da6d52c50a8a68fe939e0bc379ea7a6b
Reviewed-on: https://go-review.googlesource.com/c/vulndb/+/342894
Trust: Julie Qiu <julie@golang.org>
Run-TryBot: Julie Qiu <julie@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Roland Shoemaker <roland@golang.org>
diff --git a/README.md b/README.md
index 4c4b875..c0fae23 100644
--- a/README.md
+++ b/README.md
@@ -16,8 +16,11 @@
 
 https://storage.googleapis.com/go-vulndb/
 
-An `index.json` file maps module paths to last modified timestamps. For each
-module, a `NAME.json` file contains a list of vulnerability entries.
+An `index.json` file maps module paths to last modified timestamps
+([link](https://storage.googleapis.com/go-vulndb/index.json)).
+
+For each module, a `NAME.json` file contains a list of vulnerability entries
+([example](https://storage.googleapis.com/go-vulndb/golang.org/x/crypto.json)).
 
 Note that this path and format are provisional and likely to change until an
 approved proposal.