Spread route slug and folder slug

[BRA1L0R]

NextJS supports folder slugs and spread slugs while we only support file slugs:

• pages/[username]/settings.js → /:username/settings (/foo/settings)
• pages/post/[...all].js → /post/* (/post/2020/id/title)

[BRA1L0R]

Need to override the regexp function in tinyhttp. This could be useful.

Moving into 0.2 due to not being a strict priority + time consuming