doc: add glossary.md

Related issue: https://github.com/nodejs/node/issues/26718.

Todo

I want to add primordials, but I have no idea what it means.

cc @refack @BridgeAR

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines