Deprecation of the "Preview" feature (use "Regen" instead)

[bionota]

The Preview Feature code is rather complex and spread throughout the main function of the script.

This feature has not been tested thoroughly in a while now, and may not work as expected in some cases of repeated preview generations.

(I) Kill the Preview Feature code in favour of focused maintenance on the Regeneration Feature. Both these features accomplish the same in the end: the make a new request and leave commented-out entries of the request & response in the history file.

So, really, we get to have a less complex code and instead prefer to use the Regen Feature which is already implemented and is easier to maintain and test, after all.

However, there may be some other functions which rely on the Preview Feature code, so the code must be removed slowly and cautiously to not fall into regressions on other functions.

(II) Alternatively, we may just mark the Preview Feature as deprecated in the documentation and help, and leave the code fail or behave unexpectedly in complex usage cases as time goes on.

The latter (II) is not the optimal path, and as the project may reduce active development in the near future, we must first consider if (I) is worth developer efforts.

[bionota]

.The last version of the script which has got the "Preview Feature" code is 0.87.9:

https://github.com/mountaineerbr/shellChatGPT/tree/9176c4ae53c30f9d70e18d52ca7a19174aa13ba3

Use the REGEN FEATURE instead in newer releases!