[feat] add prerender.createIndexFiles option

[bfanger]

Fixes #1443

Usage in svelte.config:

kit: {
  prerender: {
    subfolders: false,
  },
   ...

Setting the kit.prerender.subfolders setting to false (default is true) will change the filename generation from "/about/index.html" to "/about.html"

Inspiration for the subfolders name came from nuxt:
https://nuxtjs.org/docs/configuration-glossary/configuration-generate/#subfolders

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Latest commit: 8504a47

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[Rich-Harris]

Thank you, and apologies for not getting round to this PR until now. One thing I'm not 100% sure about is the subfolders name — something about it feels a little non-descriptive. What about something like createIndexFiles?

[bfanger]

Apology is appreciated.
I agree that the naming could be better, but don't think createIndexFiles is it, that name makes sense from the kit codebase standpoint, but from a user perspective it's about is not generating folders, the index files are a byproduct..

if we change the config from a boolean to an enum, that show the intent better:

routeOutput: 'file' | 'folder'

What do you think?

[Rich-Harris]

I think a boolean makes more sense to be honest. We discussed in the maintainers chatroom and decided to go with createIndexFiles — it's the sort of thing that's easy to find in the docs when you start looking for information about index.html

[isapir]

Is kit.prerender.subfolders: false still a thing?

I get an error:

Error: Unexpected option config.kit.prerender.subfolders

I have this in svelte.config.js:

/**
 * from https://kit.svelte.dev/docs/adapter-static
 */
import adapter from '@sveltejs/adapter-static';

export default {
	kit: {
		adapter: adapter({
			// default options are shown. On some platforms
			// these options are set automatically — see below
			pages: 'build',
			assets: 'build',
			fallback: null,
			precompress: false,
			strict: true
		}),
		prerender: {
			subfolders: false,
		},
	}
};

[bfanger]

// src/routes/+layout.js
export const trailingSlash = 'always';

https://kit.svelte.dev/docs/page-options#trailingslash