chore: add output restriction to prompt guidelines

The modification ensures that only the desired commit message is returned, preventing additional text in the output.

Author: vgrichina

prompts/commit_prompt.txt

@@ -9,3 +9,5 @@ For better commit messages, consider:
 Your commit message should describe what was changed and why.
 
 If the change is related to a specific issue or feature request, please mention it.
+
+IMPORTANT: Don't output any other text besides desired commit message.

prompts/conventional_commit.txt

@@ -22,3 +22,5 @@ Examples:
 
 For more complex changes, you can add a blank line after the first line, 
 followed by a more detailed description.
+
+IMPORTANT: Don't output ant other text besides generated commit message.