Yes, it is fair to fire you for _any reason_ during the probation period (ok, maybe not for your ethnicity or religious reasons etc - but this is not what has happened here).
It is also fair for you to leave on a short notice during the probation period for no reason. It is a two way street.
Don't try to read more into this situation than what it really is. Either party did not like the other, no big deal, this happens. Much better to leave early than to suffer through a longer period for nothing. Enjoy Firefox and VS Code - I'm sure there are plenty of other companies that will allow you to use whatever tools you like for development.
Don't try to read more into this situation than what it really is. Either party did not like the other, no big deal, this happens. Much better to leave early than to suffer through a longer period for nothing. Enjoy Firefox and VS Code - I'm sure there are plenty of other companies that will allow you to use whatever tools you like for development.