Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/math_avg.md

@@ -0,0 +1,19 @@
+---
+title: math avg
+layout: command
+version: 0.59.0
+---
+
+Finds the average of a list of numbers or tables
+
+## Signature
+
+```> math avg ```
+
+## Examples
+
+Get the average of a list of numbers
+```shell
+> [-50 100.0 25] | math avg
+```
+