Bump `node-gyp` devDependency from 7 to 8
Bump `node-gyp` devDependency from 7 to 8

Breaking for contributors, as it drops support of Python 2. We need
`node-gyp` >= 8.4.0 for VS 2022 support, as used in the GHA
`windows-latest` runner.

Level/leveldown,Level/leveldown,Level/leveldown