User guide layout (#5016)

- Modified CSS: font-size, colors, margins...

- Added an ArticleContent Component that will be used for the changelog
and user guide articles, which contains the styles for each titles,
paragraphs, images etc.

- Added link to User Guide in footer

- Added a UserGuideWarning Component: 

<img width="332" alt="Screenshot 2024-04-17 at 18 14 48"
src="https://github.com/twentyhq/twenty/assets/102751374/0f5c601b-a2c0-4c63-baeb-1990d65fc332">

- Added a UserGuideEditContent Component:

<img width="394" alt="Screenshot 2024-04-17 at 18 16 24"
src="https://github.com/twentyhq/twenty/assets/102751374/6c7c3bd4-c5bb-4d02-8f93-bd99bc30ce7b">

- Added a UserGuideLink Component (for usage in MDX to allow links to
open in new tab)

- Fixed table of content

- Made responsive

---------

Co-authored-by: Ady Beraud <a.beraud96@gmail.com>
Co-authored-by: Félix Malfait <felix.malfait@gmail.com>

packages/twenty-website/src/content/user-guide/constants/UserGuideHomeCards.ts

@@ -14,19 +14,19 @@ export const USER_GUIDE_HOME_CARDS: UserGuideHomeCardsType[] = [
     image: '/images/user-guide/home/what-is-twenty.png',
   },
   {
-    url: 'create-a-workspace',
+    url: 'create-workspace',
     title: 'Create a Workspace',
     subtitle: 'Custom objects store unique info in workspaces.',
     image: '/images/user-guide/home/create-a-workspace.png',
   },
   {
-    url: 'import-your-data',
+    url: 'import-export-data',
     title: 'Import your data',
     subtitle: 'Easily create a note to keep track of important information.',
     image: '/images/user-guide/home/import-your-data.png',
   },
   {
-    url: 'custom-objects',
+    url: 'objects',
     title: 'Custom Objects',
     subtitle: 'Custom objects store unique info in workspaces.',
     image: '/images/user-guide/home/custom-objects.png',