n-api: initialize a module via a special symbol
Much like regular modules, N-API modules can also benefit from having a special symbol which they can expose.
Fixes: https://github.com/nodejs/node/issues/19845
Checklist
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make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
tests and/or benchmarks are included -
documentation is changed or added -
commit message follows commit guidelines