Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/math_stddev.md

@@ -0,0 +1,28 @@
+---
+title: math stddev
+layout: command
+version: 0.59.0
+---
+
+Finds the stddev of a list of numbers or tables
+
+## Signature
+
+```> math stddev --sample```
+
+## Parameters
+
+ -  `--sample`: calculate sample standard deviation
+
+## Examples
+
+Get the stddev of a list of numbers
+```shell
+> [1 2 3 4 5] | math stddev
+```
+
+Get the sample stddev of a list of numbers
+```shell
+> [1 2 3 4 5] | math stddev -s
+```
+