Shell: Start writing a man page

This patch adds two man pages describing the parts of the shell that
have been so far finalised.

Base/usr/share/man/man1/Shell.md

@@ -0,0 +1,40 @@
+## Name
+
+`Shell` - Shell, the command language interpreter
+
+## Synopsis
+
+```**sh
+$ Shell [--skip-shellrc]
+$ Shell [--skip-shellrc] command_file [arguments...]
+$ Shell [--skip-shellrc] -c command_string [arguments...]
+```
+
+## Description
+
+The `Shell` utility is a command language interpreter, which reads commands from either a command string, a specified file, or the standard input.
+The command language shall be described in [`Shell`(5)](../man5/Shell.md), _The Shell Command Language_.
+
+Any extra arguments passed into `arguments` are placed in the local variable `$ARGV` and can also be accessed through the special variable `$*`.
+
+**NOTE**:
+
+The `Shell` utility does not promise POSIX `sh` interoperability.
+
+## Options
+
+* `-c`, `--command-string`: Executes the given string as a command and exits
+* `--skip-shellrc`: Skips running the initialisation file (at `~/.shellrc`)
+
+## Examples
+
+```sh
+# Start an interactive REPL, ignoring the shellrc
+Shell --skip-shellrc
+
+# Execute a given string
+Shell -c 'rm foo*'
+
+# Execute the contents of a file with some arguments
+Shell foo a b c
+```