Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/split_chars.md

@@ -0,0 +1,19 @@
+---
+title: split chars
+layout: command
+version: 0.59.0
+---
+
+splits a string's characters into separate rows
+
+## Signature
+
+```> split chars ```
+
+## Examples
+
+Split the string's characters into separate rows
+```shell
+> 'hello' | split chars
+```
+