Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/str_kebab-case.md

@@ -0,0 +1,38 @@
+---
+title: str kebab-case
+layout: command
+version: 0.59.0
+---
+
+converts a string to kebab-case
+
+## Signature
+
+```> str kebab-case ...rest```
+
+## Parameters
+
+ -  `...rest`: optionally convert text to kebab-case by column paths
+
+## Examples
+
+convert a string to kebab-case
+```shell
+> 'NuShell' | str kebab-case
+```
+
+convert a string to kebab-case
+```shell
+> 'thisIsTheFirstCase' | str kebab-case
+```
+
+convert a string to kebab-case
+```shell
+> 'THIS_IS_THE_SECOND_CASE' | str kebab-case
+```
+
+convert a column from a table to kebab-case
+```shell
+> [[lang, gems]; [nuTest, 100]] | str kebab-case lang
+```
+