[icu] Add version.gni.

The file version.gni contains a declaration of the ICU major version
number.

This declaration is useful in Fuchsia, for libraries that get configured
differently based on this value.

(This change could be absorbed into Chromium's ICU version)

Change-Id: I0494741b7faf14174e320393b48aee2eb27650f3
Reviewed-on: https://fuchsia-review.googlesource.com/c/third_party/icu/+/404174
Reviewed-by: Fabrice de Gans-Riberi <fdegans@google.com>
Reviewed-by: Konstantin Pozin <kpozin@google.com>
2 files changed