Trailing slash configuration

[rmarscher]

I think waku probably needs a trailing slash configuration that build adapters can try to follow when adapting the output for how that platform/runtime handles static file routing since that is platform specific. ChatGPT gave me this summary of the trailingSlash config options in a few meta frameworks:

Framework	Config Option	Default	Values
Next.js	trailingSlash	false	true, false
Nuxt.js	router.trailingSlash	undefined	true, false, undefined
Gatsby	trailingSlash	"always"	"always", "never", "ignore"
SvelteKit	kit.trailingSlash	ignore	"always", "never", "ignore"
Remix	N/A	N/A	Custom middleware or route handling

[dai-shi]

cc @sandren who has once raised it, but it's postponed.
I need think about at which layer this feature would be added.