Auto-generate markdown command docs (#4451)

* Finish updating

* a couple improvements

* Update renames

* cleanup examples

docs/commands/str_trim.md

@@ -0,0 +1,59 @@
+---
+title: str trim
+layout: command
+version: 0.59.0
+---
+
+trims text
+
+## Signature
+
+```> str trim ...rest --char --left --right --all --both --format```
+
+## Parameters
+
+ -  `...rest`: optionally trim text by column paths
+ -  `--char {string}`: character to trim (default: whitespace)
+ -  `--left`: trims characters only from the beginning of the string (default: whitespace)
+ -  `--right`: trims characters only from the end of the string (default: whitespace)
+ -  `--all`: trims all characters from both sides of the string *and* in the middle (default: whitespace)
+ -  `--both`: trims all characters from left and right side of the string (default: whitespace)
+ -  `--format`: trims spaces replacing multiple characters with singles in the middle (default: whitespace)
+
+## Examples
+
+Trim whitespace
+```shell
+> 'Nu shell ' | str trim
+```
+
+Trim a specific character
+```shell
+> '=== Nu shell ===' | str trim -c '=' | str trim
+```
+
+Trim all characters
+```shell
+> ' Nu   shell ' | str trim -a
+```
+
+Trim whitespace from the beginning of string
+```shell
+> ' Nu shell ' | str trim -l
+```
+
+Trim a specific character
+```shell
+> '=== Nu shell ===' | str trim -c '='
+```
+
+Trim whitespace from the end of string
+```shell
+> ' Nu shell ' | str trim -r
+```
+
+Trim a specific character
+```shell
+> '=== Nu shell ===' | str trim -r -c '='
+```
+