It aligns with the changes proposed added in Gutenberg: https://github.com/WordPress/gutenberg/pull/33293.
The idea here is to split the growing webpack config into two parts: blocks and packages.
We need to add handling for JavaScript files that are going to be used with blocks on the frontend. They didn't work quite well with the current setup for entry points created for packages.
As part of the effort, it adds support for `viewScript` in `block.json` metadata file that is later translated to `$view_script` in `WP_Block_Type` class and exposed as `view_script` from the REST API endpoint for block types.
Props youknowriad, desrosj, aristath.
Fixes#53690.
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