feat(username): add aliases option (#5855)

* Create place to put it in the config

* Initial functional version

* Fix grammar

* Add option documentation to README

* Add test for two aliases and emoji translation

* Remove println

* Rewrite match as iflet

* Improve converting the reference

* Format file

* Try to restore autoformat of markdown

* Replace toml:Map with concrete IndexMap

* Update schema

* Add option that got lost

docs/config/README.md

@@ -4505,6 +4505,7 @@ these variables, one workaround is to set one of them with a dummy value.
 | `format`          | `'[$user]($style) in '` | The format for the module.                                |
 | `show_always`     | `false`                 | Always shows the `username` module.                       |
 | `disabled`        | `false`                 | Disables the `username` module.                           |
+| `aliases`         | `{}`                    | Translate system usernames to something else              |
 
 ### Variables
 
@@ -4526,6 +4527,7 @@ style_root = 'black bold'
 format = 'user: [$user]($style) '
 disabled = false
 show_always = true
+aliases = { "corpuser034g" = "matchai" }
 ```
 
 #### Hide the hostname in remote tmux sessions