doc,deps: document how to maintain ICU in Node.js
- update v8 guide to mention ICU
- move content from the tools/icu/README.md but leave a pointer
Fixes: https://github.com/nodejs/node/issues/26108
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
documentation is changed or added -
commit message follows commit guidelines