Website UI design (#4829)

**Fixed different issues** :
 
- Multiple CSS fixes: font-size, colors, margins, z-index ...
- Fixed hover on contributor avatars
- Added link to contributors in footer
- Made the year in the footer dynamic (2023 --> 2024)
- Added name of contributor in "Thank you" section of Contributor page
- Added footer in small screens
- Made Activity Log Responsive 
- Fixed bug in "saving issues to DB", title was null everywhere. I
needed to implement an "upsert" behaviour to update the existing
database on init

**To be noted :** 

There is the following bug on production happening on mobile when you
refresh a second time :

<img width="1440" alt="Screenshot 2024-04-05 at 01 30 58"
src="https://github.com/twentyhq/twenty/assets/102751374/b935b07a-63dc-463d-8dcb-070ad4ef6db0">


It seems to be related to the following issue on mdx :
[https://github.com/hashicorp/next-mdx-remote/issues/350](https://github.com/hashicorp/next-mdx-remote/issues/350)

I added the following code that fixed this bug for me in development
(this needs to be tested in production) :

```
const serialized = await serialize(content, {
    mdxOptions: {
      development: process.env.NODE_ENV === 'development',
    }
  })
```

---------

Co-authored-by: Ady Beraud <a.beraud96@gmail.com>

packages/twenty-website/src/app/_components/contributors/ProfileCard.tsx

@@ -10,6 +10,10 @@ const ProfileContainer = styled.div`
   gap: 32px;
   width: 100%;
   align-items: center;
+  @media (max-width: 600px) {
+    flex-direction: column;
+    align-items: start;
+  }
 `;
 
 const Avatar = styled.div`
@@ -33,6 +37,10 @@ const Details = styled.div`
   flex-direction: column;
   gap: 4px;
 
+  @media (max-width: 810px) {
+    gap: 8px;
+  }
+
   .username {
     font-size: 40px;
     font-weight: 700;
@@ -42,7 +50,7 @@ const Details = styled.div`
     gap: 12px;
 
     @media (max-width: 810px) {
-      font-size: 24px;
+      font-size: 32px;
       line-height: 28.8px;
     }
   }