Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/dfr_to-lowercase.md

@@ -0,0 +1,19 @@
+---
+title: dfr to-lowercase
+layout: command
+version: 0.59.0
+---
+
+Lowercase the strings in the column
+
+## Signature
+
+```> dfr to-lowercase ```
+
+## Examples
+
+Modifies strings to lowercase
+```shell
+> [Abc aBc abC] | dfr to-df | dfr to-lowercase
+```
+