fixes#688
- the `options` subcommand of `attach` functions the same,
as the `options` subcommand of creating the normal session,
but not every option will have an effect on reattaching,
for example the `default_mode` setting would make no sense
to switch.
In the future it would make sense to be able to hot swap some
of the options on reattach, but we are not able to do that yet,
for example the `default_shell` one.
Eg:
```
zellij attach <session-name> options --theme <theme>
```
9a5a315aee