This commit also introduces a convention where these common JS config files, including `package.hugo.json`, gets mounted into:
```
assets/_jsconfig
´``
These files mapped to their real filename will be added to the environment when running PostCSS, Babel etc., so you can do `process.env.HUGO_FILE_TAILWIND_CONFIG_JS` to resolve the real filename.
But do note that `assets` is a composite/union filesystem, so if your config file is not meant to be overridden, name them something specific.
This commit also adds adds `workDir/node_modules` to `NODE_PATH` and `HUGO_WORKDIR` to the env when running the JS tools above.
Fixes#7644Fixes#7656Fixes#7675
Add a new pipe called TranspileJS which uses the Babel cli. This makes it possible for users to write ES6 JavaScript code and transpile it to ES5 during website generation so that the code still works with older browser versions.
Fixes#5764
