[feature] new themes, new functionnality

[apoleon33]

TODO-LIST

• new theme: Kappa (4cdf057)
• new theme: Omegachad (333cf33 and Missing theme in the theme selector ? #39 )
• new theme: Minimalist (5cf8a6e)
  make images clickable (see [feature] Make theme images redirect to their github repository #43 ) see [feature] make theme images clickable #45

Questions

• Does Theme order matter?
• I took the images from their respective repositories, should I take them from somewhere else?
• Would multiple pr instead of one be preferable?