Operation request: Prepend/append text

## Summary

Especially when using the fork or the subsection operation, it would be useful to be able to

1. Extract relevant parts
2. Modify them
3. Wrap them in surrounding text

The last step here is rather clunky at the moment, since it involves having to whip out find and replace regex which simply match everything

Up to step 2

Current workaround for step 3, notice how the regex is quite odd since `.*` doesn't work as expected.


### Example

https://gchq.github.io/CyberChef/#recipe=Subsection('%20%5C%5Cd%2B',true,true,false)Find_/_Replace(%7B'option':'Regex','string':'(%5C%5Cd%2B)'%7D,'$1%201',true,false,true,false)Sum('Space')Find_/_Replace(%7B'option':'Regex','string':'%5B%5E%5D%2B'%7D,'%20$%26',true,false,true,true)&input=bWVzc2FnZSBHYW1lQWN0aW9uIHsKICAgIG9uZW9mIGFjdGlvbiB7CiAgICAgICAgQ2xpZW50UGxheWVyTW92ZSB1aW50MzIgY19wbGF5ZXJfbW92ZSA9IDA7CiAgICAgICAgU2VydmVyUGxheWVyTW92ZSBzX3BsYXllcl9tb3ZlID0gMTsKCiAgICAgICAgQ2xpZW50UGxheWVyVXBkYXRlIGNfcGxheWVyX3VwZGF0ZSA9IDI7CiAgICAgICAgU2VydmVyUGxheWVyVXBkYXRlIHNfcGxheWVyX3VwZGF0ZSA9IDM7CiAgICB9Cn0

Start by examining the existing Fork and Subsection operations and the linked CyberChef recipe to understand how extracted text is currently modified and wrapped. Done means providing a way to prepend and append surrounding text without the workaround regex, with behavior covering the extraction and modification workflow described in the issue.

Written by the indexing model from the issue text.