missing `mdbook` dependencies

[amtoine]

i followed the instructions to build the server and get

>_ mdbook serve --open
2023-04-10 12:53:17 [INFO] (mdbook::book): Book building has started
2023-04-10 12:53:17 [WARN] (mdbook::preprocess::cmd): The command wasn't found, is the "admonish" preprocessor installed?
2023-04-10 12:53:17 [WARN] (mdbook::preprocess::cmd): 	Command: mdbook-admonish
2023-04-10 12:53:17 [ERROR] (mdbook::utils): Error: Unable to start the "katex" preprocessor. Is it installed?
2023-04-10 12:53:17 [ERROR] (mdbook::utils): 	Caused By: No such file or directory (os error 2)

which can be solved with

cargo install mdbook-admonish mdbook-katex

😉