Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/dfr_shift.md

@@ -0,0 +1,23 @@
+---
+title: dfr shift
+layout: command
+version: 0.59.0
+---
+
+Shifts the values by a given period
+
+## Signature
+
+```> dfr shift (period)```
+
+## Parameters
+
+ -  `period`: shift period
+
+## Examples
+
+Shifts the values by a given period
+```shell
+> [1 2 2 3 3] | dfr to-df | dfr shift 2 | dfr drop-nulls
+```
+