Base: Document new Shell prompt formatting options

Author: https://github.com/adamjoer
Commit: 5fb748b333
Pull-request: https://github.com/SerenityOS/serenity/pull/21589
Reviewed-by: https://github.com/alimpfard

Base/usr/share/man/man7/Shell-vars.md

@@ -63,6 +63,13 @@ The value of this variable is used to generate a prompt, the following escape se
 - `\\u`: the current username
 - `\\w`: a collapsed path (relative to home) to the current directory
 - `\\X`: reset style (foreground and background color, etc)
+- `\\t`: Current time in the 24-hour format HH:MM:SS
+- `\\T`: Current time in the 12-hour format HH:MM
+- `\\@`: Current time in the 12-hour format HH:MM AM/PM
+- `\\D{format}`: Current time, where the string _format_ is passed on to `Core::DateTime::to_string`. If _format_ is empty, a default format string is chosen.
+- `\\j`: The number of jobs currently managed by the shell
+- `\\!`: The history number of the next command to be run
+- `\\\\`: A backslash
 
 Any other escaped character shall be ignored.