Support hybrid output file format

[NSeydoux]

What package is the feature request related to?

typedoc-plugin-markdown

Background

Up until v4 of the typedoc-plugin-markdown, it was possible to have the entry document be in a different file format that the rest of the output. Specifically, in my case, we have a manually written restructured text (.rst) index file, and then generated all the API docs in markdown pointing back to that index.rst. We then consumed the whole in a follow-up step to add our own navigation, among other things.

This behavior is no longer possible in v4, where all the generated files must be of the same format. The legacy entryDocument configuration, which allowed to have a file name and its extension, is no longer supported, so the global fileExtension is applied to the entryFileName as well as all the other generated files, which breaks our workflow.

Proposed solution

An additional configuration option, entryFileExtension, could override the default fileExtension, allowing to have a custom index file as we do. Would that be an acceptable addition to the configuration API to maintain previous capabilities?