Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/str_capitalize.md

@@ -0,0 +1,33 @@
+---
+title: str capitalize
+layout: command
+version: 0.59.0
+---
+
+capitalizes text
+
+## Signature
+
+```> str capitalize ...rest```
+
+## Parameters
+
+ -  `...rest`: optionally capitalize text by column paths
+
+## Examples
+
+Capitalize contents
+```shell
+> 'good day' | str capitalize
+```
+
+Capitalize contents
+```shell
+> 'anton' | str capitalize
+```
+
+Capitalize a column in a table
+```shell
+> [[lang, gems]; [nu_test, 100]] | str capitalize lang
+```
+