Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/math_eval.md

@@ -0,0 +1,23 @@
+---
+title: math eval
+layout: command
+version: 0.59.0
+---
+
+Evaluate a math expression into a number
+
+## Signature
+
+```> math eval (math expression)```
+
+## Parameters
+
+ -  `math expression`: the math expression to evaluate
+
+## Examples
+
+Evalulate math in the pipeline
+```shell
+> '10 / 4' | math eval
+```
+