Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/dfr_replace.md

@@ -0,0 +1,24 @@
+---
+title: dfr replace
+layout: command
+version: 0.59.0
+---
+
+Replace the leftmost (sub)string by a regex pattern
+
+## Signature
+
+```> dfr replace --pattern --replace```
+
+## Parameters
+
+ -  `--pattern {string}`: Regex pattern to be matched
+ -  `--replace {string}`: replacing string
+
+## Examples
+
+Replaces string
+```shell
+> [abc abc abc] | dfr to-df | dfr replace -p ab -r AB
+```
+