Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/url_scheme.md

@@ -0,0 +1,28 @@
+---
+title: url scheme
+layout: command
+version: 0.59.0
+---
+
+gets the scheme (eg http, file) of a url
+
+## Signature
+
+```> url scheme ...rest```
+
+## Parameters
+
+ -  `...rest`: optionally operate by cell path
+
+## Examples
+
+Get scheme of a url
+```shell
+> echo 'http://www.example.com' | url scheme
+```
+
+You get an empty string if there is no scheme
+```shell
+> echo 'test' | url scheme
+```
+