Allow to provide a fix article identifier

[nvuillam]

Today with your great app we can generate articles preview links using indexes

But what if we want a fixed list of articles, not depending on when they have been posted ?

For example, it would help a lot that if for article https://medium.com/p/62ebab422c1 we could created a preview like that:

<a target="_blank" href="https://github-readme-medium-recent-article.vercel.app/medium/p/62ebab422c1"><img src="https://github-readme-medium-recent-article.vercel.app/medium/62ebab422c1" alt="My identified article">

Thanks :)