Add profiles documentation (#8311)

* Add profiles documentation

* Fix order and reword some things

plugins/profiles/README.md

+# profiles plugin
+
+This plugin allows you to create separate configuration files for zsh based
+on your long hostname (including the domain).
+
+To use it, add profiles to the plugins array of your zshrc file:
+
+```sh
+plugins=(... profiles)
+```
+
+It takes your `$HOST` variable and looks for files named according to the
+domain parts in `$ZSH_CUSTOM/profiles/` directory.
+
+For example, for `HOST=host.domain.com`, it will try to load the following files,
+in this order:
+
+```text
+$ZSH_CUSTOM/profiles/com
+$ZSH_CUSTOM/profiles/domain.com
+$ZSH_CUSTOM/profiles/host.domain.com
+```
+
+This means that if there are conflicting settings on those files, the one to take
+precedence will be the last applied, i.e. the one in host.domain.com.