n-api: add napi_get_version
Add napi_get_version function so that addons can query the level of N-API supported.
Fixes: https://github.com/nodejs/abi-stable-node/issues/231
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]
Affected core subsystem(s)
n-api