Add error message when target directory of --sprite-input and/or --sprite-output is not exist.

[naogify]

Describe the bug

When I run charites build style.yml style.json --sprite-input noExistDir --sprite-output noExistDir, I don't get any error message even if the directory specified in the --sprite-input and/or --sprite-output is missing.

To Reproduce

In the example below, noExistDir is a directory that does not exist.

charites build style.yml style.json --sprite-input icons --sprite-output noExistDir

charites build style.yml style.json --sprite-input icons --sprite-output noExistDir

Expected behavior

It should show error message.

Screenshots

Charites Version:

• Charites version: 0.1.3 (It is on main branch)

Desktop (please complete the following information):

• OS: Mac