Adding DraculaTheme

[ArturoRomanelli]

I recently switched to dracula theme, and I wanted an app that allowed me to track my habits with this particular theme. Since I found none, but found this useful app, I wanted to contribute to expanding the Dracula Theme pool.

This pull request mostly does the job to add dracula theme, trying as much as possible to be coherent with the theme guideline and to style everything from ThemeData. I tried to replace hard-coded values of colors/fontstyles with theme variables, in order not to add logic to manage the "special" case Dracula Theme.

Please feel free to edit/request edits as you wish, I will try to respond as soon as possible :)

[xpavle00]

Hey, thanks for contributing.
But this seems like so many changes due to just one theme. Many of these look like just formatting of code or removing comments(which makes it hard to review). These things are unrelated to the intended change and shouldn't be part of the PR. Also, in visual changes, it would be nice to have screenshots.
I am thinking that it would be maybe better to add some functionality to load the theme from XML or so (I will think it through) to avoid all these rewrites for future themes.

[ArturoRomanelli]

Hi, thank you for looking at the pull request!

Probably I have different settings on code formatting, do you mind share the yaml file to see if I can somehow refine the pull request with only the important changes?

Other than that, a lot of changes were made because a lot of times widgets were not following the theme, but had hardcoded sizes or colors.

Tonight or in the following days I will try to upload some screenshots

The theme from XML would be a good idea, if implemented.