Update colors theme

[EmmanuelDrouin]

Design improvement V1

• New colors theme in nuxt.config
• New variables.scss
• New alert box (info) Design
• New side-menu Design
• Services:
  • Update h1 service name
  • Update h2 into service tab
  • Services list homepage: replace h2 titles by h3
  • Commented code overwriting markdown titles

Todo:

• [x] Design tables
• [x] Design "code" elements
• [x] Design buttons
• [x] Improve menu-group
• [x] Design Faucet

[EmmanuelDrouin]

@antho1404 ready for review