feat: support filters from external library

[derberg]

Description

• support filters from an external library. New template config parameter is added, filters that accepts an array of libraries that you can additionally register as filters for your template.
• generator now reads any function and then registers it as a filter so it is easier to write functions for templates and test them
• extracted whole logic related to filters registration to a separate file as generator.js is super overwhelming so using the opportunity that I worked on filters I moved them out

How to test:
./cli.js test/docs/streetlights.yml https://github.com/derberg/html-template/#use-filters-lib -o output --force-write

Migration Guide

Your templates will not work with the latest generator. In your template, in filter directory you need to refactor your functions to follow new structure or remove filters that are already extracted to https://github.com/asyncapi/generator-filters

• To use https://github.com/asyncapi/generator-filters you need to add the following property to your template configuration file

  "filters": [
    "@asyncapi/generator-filters"
  ]

and have this package in package.json dependencies

 "@asyncapi/generator-filters": "^1.0.0"

• To refactor your existing filters just make sure your filters are normal JS functions and you export them as part of the module. Have a look on one of our official templates to see how new filters look like https://github.com/asyncapi/html-template/blob/master/filters/all.js. You do not have to change the logic, they just need to be refactored as they no longer need Nunjucks environment as input, which also means they are much easier to test now

Related issue(s)
Fixes #212

[fmvilas]

Left some suggestions. Great stuff!

[derberg]

@fmvilas your suggestions are in, thanks! I also removed one not needed function that was left from my development. What about the config? nothing agains? should I move other config values there with this PR or?

[derberg]

@fmvilas forget my last question, I'm removing node-config as its purpose if for apps rather than libraries and it doesn't work nice in a scenario when the generator is used as a library, only complicates live. I will bring back global variable FILTERS_DIRNAME and pass it to the filters function like others arguments.

[fmvilas]

Looks great! Minor stuff 👍

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!

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[asyncapi-bot]

🎉 This PR is included in version 0.41.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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