Instead of using core/snapshot_creator.rs, instead two crates are
introduced which allow building the snapshot during build.rs.

Rollup is removed and replaced with our own bundler. This removes
the Node build dependency. Modules in //js now use Deno-style imports
with file extensions, rather than Node style extensionless imports.

This improves incremental build time when changes are made to //js files
by about 40 seconds.

Closes #2720

It didn't deliver the expected performance improvements, so let's go
back and use Rust defaults again.

This reverts commit 4232c89c.

Adds note about colors module location change in deno_std

This is a regression on several some features in the fetch API. To bring
these back @stardazed/streams simply needs to be ported to TS and
included in the //js directory.

Towards #2608

This removes dispatch_flatbuffers as it is now unused. There are still a
few places where msg_generated is used: ErrorKind and MediaType. These
will be dealt with later.

* Revert "port more ops to JSON (#2809)"

This reverts commit 137f3373.

* Revert "port ops to JSON: compiler, errors, fetch, files (#2804)"

This reverts commit 79f82cf1.

* Revert "Port rest of os ops to JSON (#2802)"

This reverts commit 5b2baa5c.

Similar to React's CONTRIBUTING.md
https://github.com/facebook/react/blob/master/CONTRIBUTING.md