added color themes and functionality to change them as well

[ujjwalshrma]

This change adds the functionality to select a different colorscheme from the dropdown.

I added individual CSS files for each theme to not clutter the theme.css or any other CSS file.

[Markonis]

Hey I love this idea! 👏 Here are a few comments:

• I would suggest installing the "EditorConfig for VS Code" extension so that we get consistent formatting. It's kind of like prettier, but much less complex and not as strict.
• How do you feel about implementing the theme selection in the same way you can select the repository for typing? Not a requirement, just curious what you think? Maybe we can add a second question after choosing the repo to be like: "Oh would you like to change your theme?" And then you choose from one of the ones you implemented?

[ujjwalshrma]

• For the first point Marko, I was using Neovim, that's why the formatting was a bit off.

• I appreciate your points but I thought that theme selection can be a bit easier, I tried to implement it like how it's done in "MonkeType". On the bottom of monkey type you can just simply change your theme by selecting it, also I think a dedicated question just for a theme would be too much as for VSCode and other editors we can set the themes by ourselves and the editor doesn't suggest us. (that's my analogy). I can also change the "Default" to "Select Theme" in the dropdown so it'll be more obvious for users to identify the feature.