Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/dfr_slice.md

@@ -0,0 +1,24 @@
+---
+title: dfr slice
+layout: command
+version: 0.59.0
+---
+
+Creates new dataframe from a slice of rows
+
+## Signature
+
+```> dfr slice (offset) (size)```
+
+## Parameters
+
+ -  `offset`: start of slice
+ -  `size`: size of slice
+
+## Examples
+
+Create new dataframe from a slice of the rows
+```shell
+> [[a b]; [1 2] [3 4]] | dfr to-df | dfr slice 0 1
+```
+