Reorganize author section

[nanxstats]

Two things:

• Move the authors section from the landing page to a non-landing page, such as the preface (introduction) chapter like https://mastering-shiny.org/preface.html did.
• A better display of the authors and contributors instead of using a two-column table (with many values missing). Again, good example from the link above.

[nanxstats]

Closed by https://github.com/elong0527/r4csr/pull/34