Rename configurations

[shuding]

I'm working on the docs and noticed some option names that can be improved for better consistency and accuracy. This will be another breaking change for v2, hopefully the last one.

• banner.text → banner.content
• footer.text → footer.content
• editLink.text → editLink.content
• feedback.link → feedback.content
• bodyExtraContent → main.extraContent (in the future we can configure the main content area here)
• i18n.text → i18n.name
• projectChat → chat
• github → removed, use project.link

[dimaMachina]

@shuding added new throughout for v3

footer: ReactNode | FC | { text: ReactNode | FC }

search: ReactNode | FC | { emptyResult: ..., error: ..., loading: ..., placeholder: ... }

toc: ReactNode | FC | { extraContent: ..., float: ..., title: ... }

editLink: ReactNode | FC | { text: ... }

[dimaMachina]

closed by #2250

https://github.com/shuding/nextra/releases/tag/nextra%403.0.0-alpha.0