Adds Theme Functionality

[Sir-Kam]

Though I've seen no one mention this in the issues, I decided to mess around and implement it just for myself. So I thought I'd put forth a request for this addition to be merged, as I imagine others might like it :) ~

New Additions

Themes

• Adds 'ttkbootstrap' package to the requirements.txt which allows for easy theme handling. Trying to create a solution for coloring the UI without it, while possible, was kinda fiddly- so I opted to use this package instead.
• Using 'ttkbootstrap', 3 typical UI themes have been made usable: Light, Dark, and Black. Light is quite similar to how the UI is colored currently, Dark is your normal dark mode, and Black is a darker Dark.
• An option to change the theme has been added to the Settings window. The theme will update the UI colors when changed and the selected theme is saved to config.

Misc

Settings Window Screen Position

• The settings window will now open at the current position of the main (root) window. Where previously if the main window was moved to another monitor, then when the settings window was opened, it would be shown in the default position (where the main was initially shown).

[BigBoiCJ]

Woops! Sorry, I've been away for a while! Thanks for making this, I'll have a look at it!

[BigBoiCJ]

And I still haven't looked at it and I'm still busy... what a bad 'maintainer' I am