Add new command ``` tt doctor```

I think we can add new command tt doctor.
It functionality will be similar to brew doctor.
In other words it will check config for existance/ syntax errors. Also check directories(specified in config) for existance/ if we have enough rights to use them/ if they are not specified. Also can check values in config ( if they are reasonable/if they are not specified).
If some issues are faced tt doctor will output a warning or an error and a way to fix it. Fell free to add thoughts about it.
e.g

Warning: The following directories are not writable by your user:
/usr/local/bin

You should change the ownership of these directories to your user.
  sudo chown -R $(whoami) /usr/local/bin

And make sure that your user has write permission.
  chmod u+w /usr/local/bin

The issue does not name files, tests, or an entry point; start by reviewing the existing tt command structure and configuration handling. Done should include a doctor command that reports actionable warnings or errors for invalid or missing configuration, directory existence and permissions, and unreasonable or unspecified values.