[Feature]: Customising Footer/page overflow

[zmzlois]

What problem does this feature solve?

Make bottom props align with existing footer but not living somewhere else and needing to:

1. constraint body width (currently overflows)
2. calculate paddings to make sure the bottom align with existing footer

What does the proposed API look like?

The exposed bottom prop in layout should expose:

1. original pagination (that's footer already!)
2. additional linking (say we want to add other links)

[Timeless0911]

You can customize your theme https://rspress.dev/guide/advanced/custom-theme#redevelop-a-custom-theme.