feat: [gnoweb] Allow goldmark extentions

[stackdump]

Revisit https://github.com/gnolang/gno/pull/4186 - adding a better means to customize markdown rendering

Description

We are introducing a mechanism to allow custom Markdown rendering in gnoweb through an optional build tag and injection of a custom renderer factory.

Goals

Add setup_gnomark.go behind the gnomark build tag to register a custom Markdown renderer using Goldmark.

Allow external packages to override the default MarkdownRenderer behavior by injecting a RenderFactory.

Decouple renderer instantiation from hardcoded logic in NewRouter.

Changes

New file: contribs/gnodev/cmd/gnodev/setup_gnomark.go

Registers a RenderFactory for Markdown rendering using goldmark.

Uses gnoweb.SetRenderFactory() in init() when gnomark tag is set.

gno.land/pkg/gnoweb/app.go

Adds RenderFactory as a configurable function.

Introduces SetRenderFactory() and a default implementation DefaultMarkdown().

Replaces inline Goldmark setup in NewRouter() with the factory.

gno.land/pkg/gnoweb/markdown.go

Renames markdown → Markdown and logger → Logger (exported for custom usage).

Adjusts Render() to use the exported fields, enabling injected implementations to be compatible.

Motivation

This change provides a clean extension point for advanced Markdown rendering, such as:

Custom extensions (e.g., task lists, Gno-specific syntax)

Developer-only builds with preview rendering

Future toggles for experimental render pipelines

[Gno2D2]

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Codecov Report

Attention: Patch coverage is 35.00000% with 13 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
gno.land/pkg/gnoweb/app.go	26.66%	9 Missing and 2 partials :warning:
gno.land/pkg/gnoweb/markdown.go	60.00%	1 Missing and 1 partial :warning:

:loudspeaker: Thoughts on this report? Let us know!

[stackdump]

I don't believe this is the right approach. But don't make me wrong; I'm definitely open to extending or overriding gnoweb's rendering capability, but not in this manner.

In my opignon we should:

• pass rendering as an app options (im actually adding this in #4410)
• move most of gnodev cmd code in an app package, so external package can import it and extend/override it.
  • this app package could then take a gnoweb factory as an options, to create custom instance of gnoweb.

I need to think more about how to implement this. If the gnodev's cmd App is exposed, it will require some reworking.

In the meantime, don't hesitate to reach me out directly, especially if this is blocking you somehow.

It sounds like the above changes will provide a clean way for me to integrate in the future.

Let me know if I can help the refactor effort.

[stackdump]

closing - will watch progress on https://github.com/gnolang/gno/pull/4410