Reveal parser worker

Used as a dependency for @cognite/reveal.

Parser-worker has some parts written on Rust, so build output contains
worker files and .wasm file.

Getting started

Note that if you want to simply run the viewer you don't need to build parser-worker.
It's already used as a dependency from the NPM to have proper types
and built version is coming from Cognite CDN.
Build it only if you're about to change parser-worker and want to test local changes.

Also, you might want to build it if you need to create a build with custom PUBLIC_PATH
and host it on your own static server.

Don't forget that if you're committing your changes, you will need to publish a new NPM release and upload worker build to CDN.

$3

* Install Node
* Install Yarn
* Install Rust

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##### Windows

With Rust installed and ready to go, open a command shell and run cargo install wasm-pack

##### Linux / macOS

You can either run the same command as in Windows, or install it faster through https://rustwasm.github.io/wasm-pack/

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``bash
cd ./parser-worker
yarn
yarn build
`

In case if you need to build with custom public path,
just set the environment variable PUBLIC_PATH and run the build.

`bash
PUBLIC_PATH="https://static.server/parser-worker/" yarn build:prod
`

Notice that environment variable setting syntax differs if you use Windows.

`bash
set PUBLIC_PATH="https://static.server/parser-worker/" && yarn build:prod
`

If you set the env variable correctly, during the build you should see this printing in your console:

`
> ⬡ : Worker local build config:
> ⬡ : { publicPath: 'https://static.server/parser-worker/' }
`

Now parser-worker/dist/local folder contains the built worker and wasm files.
You can host them at your static server.

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If you want to test your own changes in worker or rust module locally,
all you need to do is to copy files from parser-worker/dist/local to some folder in examples.

You can simply use yarn local-cdn it does:

* run parser-worker build
* copy files to examples/public/local-cdn
* build viewer with publicPath pointing on 'local-cdn'
* run the examples server.

You will also need to link @cognite/reveal-parser-worker to the local version in order to get proper type declarations:

* From parser-worker/: yarn link
* From viewer/: yarn link @cognite/reveal-parser-worker

Notice that it builds the viewer with the same
public path, so you don't have to override revealEnv in examples. If you do some changes for the viewer at the same time,
you might want to run viewer build separately. For the viewer either build it with the same PUBLIC_PATH env variable, or
specify the path to worker files in examples with revealEnv (see examples/routes.tsx).

If you're not overriding the revealEnv with the path to local-cdn -
you should build the viewer with PUBLIC_PATH env variable that points on /local-cdn folder.
For example:

`bash
cd ../viewer
PUBLIC_PATH="/local-cdn" yarn build --watch
`

Make sure the path you use for building the parser-worker matches the path
you run examples on (where worker files are available).

In case if you want to test worker changes outside examples,
you still can use yarn local-cdn command,
but notice that you'll need to override path to reveal workers
with the revealEnv in your target project.

`js
import { revealEnv, Cognite3DViewer } from '@cognite/reveal';
revealEnv.publicPath = https://localhost:3000/local-cdn/;

// ... then use reveal normally ...
const viewer = new Cognite3DViewer(/.../)
``

Note, that if you make any changes in build setup, it's important to run another examples-server on a different port than local-cdn,
to have cross-domain worker initialisation in examples, and make sure both cases (same domain and different one) work fine.

See: https://github.com/cognitedata/reveal/blob/master/viewer/src/utilities/workers/WorkerPool.ts#L60-L65