Add docs for built-in plugins (fzf, zoxide)

[sxyazi]

Purpose:

To introduce users to the built-in plugins included in Yazi, explain their specific uses, and list available configuration options.

For example, the zoxide plugin includes an update_db configuration that allows Yazi to update zoxide's database when using the cd command.

This could perhaps be a subpage under Plugins (following Config).

[rohitmore07]

Hi @sxyazi
I’d love to help with the documentation. Let me know which section needs improvement or if there are new sections you'd like added!