Bug fixes and small changes to match my environment

* It’s now returning the list of all accounts
* If the secret is not valid, it’s not throwing an exception anymore,
just ignoring the account.
* Return empty for some cases, so the value is not added to the
clipboard (e.g. remaining time, error messages)
* New icons (just to match my environment)
* Check if the file exists and only display a message to create a new
file if it doesn’t exist
Updated README.md