Improve UI

[nuno-faria]

I've been working on a blog post and noticed that the interface could use an update. Here are the main changes:

• Use new fonts.
• Limit the content width.
• Add some extra spacing between sections.
• Improve TOC.
• Add a bg to tables.
• Tidy the blog index, making it look more like the Arrow blog (https://arrow.apache.org/blog/).

Some screenshots:

Before:

After:

Before:

After:

Before:

After:

[martin-g]

May I ask for an additional small improvement ?

In dark mode the source snippets are not very readable:

The same looks much better in the user guide:

[nuno-faria]

Thanks @martin-g. I forgot to add screenshots with the dark mode. Here's what it looks like now:

Let me know if this is ok.

[martin-g]

Yep! Thank you, @nuno-faria !