Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/str_downcase.md

@@ -0,0 +1,38 @@
+---
+title: str downcase
+layout: command
+version: 0.59.0
+---
+
+downcases text
+
+## Signature
+
+```> str downcase ...rest```
+
+## Parameters
+
+ -  `...rest`: optionally downcase text by column paths
+
+## Examples
+
+Downcase contents
+```shell
+> 'NU' | str downcase
+```
+
+Downcase contents
+```shell
+> 'TESTa' | str downcase
+```
+
+Downcase contents
+```shell
+> [[ColA ColB]; [Test ABC]] | str downcase ColA
+```
+
+Downcase contents
+```shell
+> [[ColA ColB]; [Test ABC]] | str downcase ColA ColB
+```
+