Select currently applied theme in the prompt

[arunvelsriram]

Related issue: #5

• Refactoring: extracted reusable functions/constants to a common place
• Upgraded inquirer-autocomplete-prompt to v1.2.0 as it had the feature to select a default value
• After applying the theme, save the theme name to <alacritty-config-dir>/.current-theme
• Get the current theme name from <alacritty-config-dir>/.current-theme file and select it in the prompt by default

(I have tested these changes in Mac OS only)

[arunvelsriram]

@rajasegar I have updated the code to use value of name in the colors configuration. However we will have to add name to all themes.

What should be the value of name in the theme yamls?

[rajasegar-c]

It will be the name of the file

[arunvelsriram]

@rajasegar I have set the name to theme filename for all themes.

I couldn't make convert.js script work. Its introducing a lot of changes and am not sure if its required or not. So I updated the name using another script (one-off script I wrote).