Update to napi-rs v2

[devongovett]

This updates the node bindings to use napi-rs v2, with the new derive macro which really simplifies generating classes and methods a lot. Also bumps Rust to the 2021 edition.

[devongovett]

This seems to be causing segfaults occasionally in my testing, and I don't know why... Might be a bug in napi-rs.

* thread #14, stop reason = EXC_BAD_ACCESS (code=1, address=0x30)
  * frame #0: 0x000000012a447af8 index.darwin-arm64.node`_rjem_je_extent_heap_remove + 328
    frame #1: 0x000000012a449734 index.darwin-arm64.node`extents_remove_locked + 244
    frame #2: 0x000000012a4483e0 index.darwin-arm64.node`extent_recycle + 472
    frame #3: 0x000000012a4481fc index.darwin-arm64.node`_rjem_je_extents_alloc + 44
    frame #4: 0x000000012a434168 index.darwin-arm64.node`arena_bin_malloc_hard + 312
    frame #5: 0x000000012a433e3c index.darwin-arm64.node`_rjem_je_arena_tcache_fill_small + 556
    frame #6: 0x000000012a45a628 index.darwin-arm64.node`_rjem_je_tcache_alloc_small_hard + 28
    frame #7: 0x000000012a4360cc index.darwin-arm64.node`_rjem_je_arena_ralloc + 1588
    frame #8: 0x000000012a42e890 index.darwin-arm64.node`_rjem_rallocx + 320
    frame #9: 0x000000012a3ec168 index.darwin-arm64.node`alloc::raw_vec::finish_grow::h1d5846dc1bf2fa94 + 80
    frame #10: 0x000000012a3f18e0 index.darwin-arm64.node`parcel_sourcemap_node::__napi_impl_helper__JsSourceMap__0::__napi__add_vlq_map::he681e7f1857f8ee1 + 3728

[DeMoorJasper]

This is so much cleaner 🤯. If the segmentation fault is not an issue with this version it looks good to me code-wise.

Sorry for the late review, this PR got buried in gh notifications

[devongovett]

Seg fault should be fixed in latest napi now