Allow for dry runs of commands

[garaiza-93]

Is your feature request related to a problem? Please describe.
Testing can be annoying, especially when a command edits a file that would have to be set up again for test cases. As far as I know, there is no easy way to test the bot other rebuilding and rerunning the bot.

Describe the feature you'd like
Allow for dry-runs of commands. When a command such as !update or !remove is run with dry-run option (perhaps a parameter), the bot would instead show the user what changes would be made. This can be shown in the log or as a steam/discord message.

Describe alternatives you've considered
I have tried minimal installations of the bot, or backing up the pricelist file that I use for testing, but that is a pain to do, especially when I have to restore changes made by the bot to these files.

Got any bounty as a reward for anyone fulfills your request?
No bounty other than my love and respect.