Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/decode.md

@@ -0,0 +1,23 @@
+---
+title: decode
+layout: command
+version: 0.59.0
+---
+
+Decode bytes as a string.
+
+## Signature
+
+```> decode (encoding)```
+
+## Parameters
+
+ -  `encoding`: the text encoding to use
+
+## Examples
+
+Decode the output of an external command
+```shell
+> cat myfile.q | decode utf-8
+```
+