Bug introduced in cea941ce

* nanoc: update command aliases

- remove deprecated commands
- update `create-site`
- add `prune`

* nanoc: update README

* nanoc: update autompletion

- update commands
- add flag options to subcommands

Fixes #7268

With `$USER`, we'd need to quote it in case special characters like `\` are present in
the $USER value, like if the user is part of an AD domain.

With `%n` the quoting is done automatically by zsh.
See http://zsh.sourceforge.net/Doc/Release/Prompt-Expansion.html#Login-information

* Added a README file for the systemadmin plugin

* Updated formatting of Functions table and split it into
"named" and "unnamed" functions for clarity

* Fixed issue with '|' characters in table by adding them in
<code> stateuents </code>

* Added \ escape characters in front of | characters

* Added README file to the dirpersist plugin

added additional details on how the plugin works.

`lstheme` command used to list only the themes listed in `$ZSH/themes/` directory. This commit adds themes in `$ZSH_CUSTOM/themes/` also to the theme listings.

These themes used an adhoc substitution of $HOME for tilde
in $PWD, but it's better to use '%~' and is less error prone.

See #7160