[prefix-trans]change "certik" to "shentu" in non-go-code files of the shentu repo

[haozhan9]

As part of the effort to change address bech32 prefix from "certik" to "shentu", please make modifications on all the non-go-code files (like markdown, script, etc.) in the repo to replace "certik" with "shentu".

Please DO NOT do the replacement mechanically and make sure the changes are reasonable.