feat!: upgrade to VuePress 2

[Kuruyia]

What does this PR do?

This updates the documentation framework to use VuePress 2. This marks version 4 of the documentation framework.

Important

The version of VuePress that is used is v2.0.0-rc.17. As its name implies, it is a Release Candidate and not a stable release.
However, because the v2 of VuePress has started 4 years ago, and that its Release Candidate started at the beginning of 2024, I considered that it should be stable enough for us to deploy it, and that it was worth putting work into the migration now.
Please do note that breaking changes can still occur until the release of the stable version 2 of VuePress, but I expect those, if they occur, to be minor.

Warning

In other repositories, there are PRs that needs to be merged beforehand:

• docs: fixes for VuePress 2 kuzzle#2553
• kuzzleio/iot-platform#371
• feat!: prepare upgrade to VuePress 2 kuzdoc#15

Other changes

• Dependencies were updated.
• CI was updated.
• VuePress plugins and theme were updated for VuePress 2 and migrated to TypeScript.
• A bunch of dependencies were either removed or replaced by a VuePress plugin.
• The Discord button has been removed.
• Font files were removed from the repo, and FontAwesome is now included as an NPM package.
• DocSearch has been updated to v3.
• Vite is now the build tool for this project.
• node-sass has been replaced with the newer sass-embedded, and deprecated stuff in the stylesheets were fixed.
• A bunch of UI tweaks.
• Other stuff I forgor

UI comparison

Before	After

[rolljee]

Great work 💪🏼