Merge pull request #757 from yahsinhuangtw/add-help-doc

Add documentation for help

docs/commands/help.md

@@ -0,0 +1,47 @@
+# help
+
+Use `help` for more information on a command.
+Use `help commands` to list all availble commands.
+Use `help <command name>` to display help about a particular command.
+
+## Examples
+
+```shell
+> help
+Welcome to Nushell.
+
+Here are some tips to help you get started.
+  * help commands - list all available commands
+  * help <command name> - display help about a particular command
+
+You can also learn more at https://book.nushell.sh
+```
+
+```shell
+> help commands
+━━━━┯━━━━━━━━━━━━━━┯━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+ #  │ name         │ description 
+────┼──────────────┼────────────────────────────────────────────────────────────────────────────────────────
+  0 │ add          │ Add a new field to the table. 
+  1 │ autoview     │ View the contents of the pipeline as a table or list. 
+  2 │ cd           │ Change to a new path. 
+  3 │ config       │ Configuration management. 
+  4 │ cp           │ Copy files. 
+  5 │ date         │ Get the current datetime. 
+...
+ 70 │ trim         │ Trim leading and following whitespace from text data. 
+ 71 │ version      │ Display Nu version 
+ 72 │ where        │ Filter table to match the condition. 
+ 73 │ which        │ Finds a program file. 
+━━━━┷━━━━━━━━━━━━━━┷━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
+```
+
+```shell
+> help cd
+Change to a new path.
+
+Usage:
+  > cd (directory)
+```
+
+