[TS] disable lint in index file

[ota42y]

We disable lint in typescript-fetch in this PR
#4110

But we doesn't disable index.ts files so we'll get error with no-cycle rule.

• index.ts import all classFiles to exporting
• When model use another models (i.e. article model have user model as author), model import another model using index.ts

So we need disable all generated file.

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
• Run the following to build the project and update samples:

  ./mvnw clean package 
  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh
  

  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  For Windows users, please run the script in Git BASH.
• File the PR against the correct branch: master, 5.1.x, 6.0.x
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

@TiFu (2017/07) @taxpon (2017/07) @sebastianhaas (2017/07) @kenisteward (2017/07) @Vrolijkx (2017/09) @macjohnny (2018/01) @topce (2018/10) @akehir (2019/07) @petejohansonxo (2019/11) @amakhrov (2020/02)

[ota42y]

travis-ci failed by docker pull error so please rebuild (I can't rebuild perhaps owner and team member only)
https://travis-ci.org/github/OpenAPITools/openapi-generator/builds/773497653

appveyor failed but master branch is failed too, so this PR is no problem

[ota42y]

I think we can merge this to 5.1.x or 6.0.x because it seems that the cause was just forgetting to add it, so it is close to a bug and many users can benefit quickly.
(If you agree that you should merge it with something other than master, recreate it.)

[TiFu]

travis-ci failed by docker pull error so please rebuild (I can't rebuild perhaps owner and team member only)

You can just close and re-open the PR to trigger the CI again ;-) Will re-open the PR in a second.

I think we can merge this to 5.1.x or 6.0.x because it seems that the cause was just forgetting to add it, so it is close to a bug and many users can benefit quickly.
(If you agree that you should merge it with something other than master, recreate it.)

@wing328 What do you think?