Fix paper page when used with trailing slash

[electrum]

No description provided.

[mosabua]

Why would the page have a trailing / in the URL? If you do that you are making the page only work correctly in the root context. Maybe better to use ./

[electrum]

The URL can be accessed in several ways

• https://prestosql.io/paper.html
• https://prestosql.io/paper
• https://prestosql.io/paper/

People often type URLs manually and thus it might end in a trailing slash. If we're going to serve the page, it shouldn't be broken. (and we don't have a choice on serving it or redirecting since that's what Netlify does)

[electrum]

Note that the entire Jekyll site is generated to be in the root context. I don't see a problem with that, since the site has a singular purpose. This is different from the documentation, which is intentionally generated to be relative, as it might be used in different contexts.

[mosabua]

I would use ./ as a fix then ..