Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/math_variance.md

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