Add new vertical digital clock widget

[CastelJeremy]

Hello, some users reported that they wanted more styles for their widget. Issue 19 and I'm willing to work on this.

I'm marking this PR as a draft because :

• This particular design was not reported.
• I'm not sure if you are interested in adding such feature or if it too many widgets would just bloat the app.
• I'm not sure if this should be the correct way to add multiple widget style.
• The preview image is missing and there is a bug when changing the text or the background color.

This is what it currently looks like :