closes https://github.com/nushell/nushell/issues/9437
cc/ @Sygmei 😉
# Description
the syntax of *captures* used in `str replace` can be confusing for
people not used to the `regex` syntax.
there is already a capture example in `help str replace`
```bash
Find and replace with fancy-regex
> 'a successful b' | str replace '\b([sS])uc(?:cs|s?)e(ed(?:ed|ing|s?)|ss(?:es|ful(?:ly)?|i(?:ons?|ve(?:ly)?)|ors?)?)\b' '${1}ucce$2'
a successful b
```
but it's really not trivial to understand the *capture* syntax...
this PR adds a simpler example only focused on *captures*
🥳
```bash
Use captures to manipulate the input text
> "abc-def" | str replace "(.+)-(.+)" "${2}_${1}"
def_abc
```
# User-Facing Changes
an example in `help str replace` to understand the syntax of *captures*.
# Tests + Formatting
- 🟢 `toolkit fmt`
- 🟢 `toolkit clippy`
- ⚫ `toolkit test`
- ⚫ `toolkit test stdlib`
# After Submitting
```
$nothing
```
bb30051006