feat(typescript-fetch): add docs support

[aheckmann]

Currently, the typescript-fetch client does not support generation of documentation. This PR adds documentation generation support and improves the generated package README.

fixes #18276
closes #18351 (abandoned)

To validate,

1. Generate the samples
   • bin/generate-samples.sh bin/configs/typescript-fetch-*.yaml
2. Open a generated typescript-fetch README.md (samples/client/petstore/typescript-fetch/builds/es6-target/README.md and click around to view the new readme, generated API documentation, model documentation and examples.
3. Run the typescript-fetch integration tests:
   ./mvnw integration-test -f samples/client/petstore/typescript-fetch/tests/default/pom.xml

Committee mentions

@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) @davidgamero (2022/03) @mkusaka (2022/04) @joscha (2024/10)

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 || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in WSL)
  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*.
  IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• File the PR against the correct branch: master (upcoming 7.x.0 minor release - breaking changes with fallbacks), 8.0.x (breaking changes without fallbacks)
• If your PR solves a reported issue, reference it using GitHub's linking syntax (e.g., having "fixes #123" present in the PR description)
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

[joscha]

Should these use File.separator as well?

[aheckmann]

I've removed the trailing slash here and added it in the web context (readme and docs files).

[joscha]

...because we seem to be using those constantly here for a local path. If we want to use the constants both in a file path context and a web context we should remove the trailing slash and add it when we use them in a web context.

[btpnlsl]

How will this interact with the withoutRuntimeChecks configuration property?

It looks like if this option is enabled models.mustache was not included in the modelTemplateFiles. See code here

[aheckmann]

Thank you - I'll push an update to exclude model docs when this option is enabled, matching the behavior of models.mustache, and also ensure this is handled in the api and readme docs.

[aheckmann]

What I ended up doing is generating model documentation whether or not withoutRuntimeChecks is enabled. It's helpful to see what input / output is expected, even if runtime checks are not enabled.