update #4455, regenerate commands' docs and update make_docs script (#4586)

* feat: update #4455, regenerate commands' docs

* chore: update make_docs script

docs/commands/export_def-env.md

@@ -16,3 +16,9 @@ Define a custom command that participates in the environment and export it from
  -  `params`: parameters
  -  `block`: body of the definition
 
+## Examples
+
+Define a custom command that participates in the environment in a module and call it
+```shell
+> module foo { export def-env bar [] { let-env FOO_BAR = "BAZ" } }; use foo bar; bar; $env.FOO_BAR
+```