Reset the file path after clear the buffer

[ccqpein]

Try to implement the issue #227 .

After (setf shell-maker-if-file-path-reset-after-clean 'reset) and manually binding the ("C-c M-o" . chatgpt-shell-clear-buffer). It will reset the shell-maker--fileto nil after I clean the buffer. So I can save the new conversation in new file.

Feel free to change it if it isn't match the design of owner.**

[ccqpein]

No problem

[xenodium]

A couple of follow-ups:

• We need to move it to shell-maker to make it compatible with the "clear" shell command: https://github.com/xenodium/chatgpt-shell/commit/a342d3398f4ffa1fce875adf9016fe63155d85ed
• Typo: https://github.com/xenodium/chatgpt-shell/commit/2f5525553a97567c1805d787880af290f8cfc926