Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/dfr_concatenate.md

@@ -0,0 +1,24 @@
+---
+title: dfr concatenate
+layout: command
+version: 0.59.0
+---
+
+Concatenates strings with other array
+
+## Signature
+
+```> dfr concatenate (other)```
+
+## Parameters
+
+ -  `other`: Other array with string to be concatenated
+
+## Examples
+
+Concatenate string
+```shell
+> let other = ([za xs cd] | dfr to-df);
+    [abc abc abc] | dfr to-df | dfr concatenate $other
+```
+