Add documentation for lines

docs/commands/lines.md

@@ -0,0 +1,28 @@
+# lines
+This command takes a string from a pipeline as input, and returns a table where each line of the input string is a row in the table. Empty lines are ignored. This command is capable of feeding other commands, such as `nth`, with its output.
+
+## Usage
+```shell
+> [input-command] | lines
+```
+
+## Examples 
+Basic usage:
+```shell
+> printf "Hello\nWorld!\nLove, nushell." | lines
+━━━┯━━━━━━━━━━━━━━━━
+ # │ value 
+───┼────────────────
+ 0 │ Hello 
+ 1 │ World! 
+ 2 │ Love, nushell. 
+━━━┷━━━━━━━━━━━━━━━━
+```
+
+One useful application is piping the contents of file into `lines`. This example extracts a certain line from a given file.
+```shell
+> cat lines.md | lines | nth 6
+## Examples
+```
+
+Similarly to this example, `lines` can be used to extract certain portions of or apply transformations to data returned by any program which returns a string.