Features/themed utilities

[Carl-Hugo]

2.1.0

• Add a Themed page in the sample app.
• Add the following themed utilities that flip from dark to light depending on the theme:
  • .bg-themed (dark: .bg-dark | Light: .bg-light)
  • .text-themed (dark: .text-light | Light: .text-dark)
  • .alert-themed (dark: .alert-dark | Light: .alert-light)
• Add the following themed utilities (inverted colors) that flip from dark to light depending on the theme:
  • .bg-themed-inverted (dark: .bg-light | Light: .bg-dark)
  • .text-themed-inverted (dark: .text-dark | Light: .text-light)
  • .alert-themed-inverted (dark: .alert-light | Light: .alert-dark)