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/_server-utils/get-posts.tsx

@@ -29,7 +29,7 @@ export interface Directory {
 async function getFiles(
   filePath: string,
   basePath: string,
-  position: number = 0,
+  position = 0,
 ): Promise<Directory> {
   const entries = fs.readdirSync(filePath, { withFileTypes: true });
 
@@ -99,13 +99,14 @@ async function parseFrontMatterAndCategory(
   return parsedDirectory;
 }
 
-export async function compileMDXFile(filePath: string, addToc: boolean = true) {
+export async function compileMDXFile(filePath: string, addToc = true) {
   const fileContent = fs.readFileSync(filePath, 'utf8');
   const compiled = await compileMDX<{ title: string; position?: number }>({
     source: fileContent,
     options: {
       parseFrontmatter: true,
       mdxOptions: {
+        development: process.env.NODE_ENV === 'development',
         remarkPlugins: [gfm],
         rehypePlugins: [rehypeSlug, ...(addToc ? [toc] : [])],
       },