feat: Create a landing page

[lucas-louis]

Description

• Add a landing page when the user arrives at the home page of IPC.
• Refactor the theme of IPC:
  • Change the style of buttons
  • Change the style of texts
  • Change the main color (the blue & red one)
• Change the routes:
  • The / route becomes /connection route
  • The / route has now the landing page

Changes include

• Bugfix (non-breaking change that solves an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (change that is not backwards-compatible and/or changes current functionality)

Checklist

• I have assigned this PR to myself
• I have added at least 1 reviewer
• I have added the needed labels
• I have linked this PR to an issue
• I have linked this PR to a milestone
• I have linked this PR to a project
• I have tested this code
• I have added / updated tests (unit / functionals / end-to-end / ...)
• I have updated the README and other relevant documents (guides...)
• I have added sufficient documentation both in code, as well as in the READMEs