I built a website using Gatsby, Contentful, and deployed on Netlify.
I am going to run this website with multiple domain aliases.

ex:
`alias1.example.com`
`alias2.example.com`

In that case, the aliases work well and the website have to show contents that belong to the own alias in Contentful.
For example, let's say the current alias is `alias1`, then the website have to fetch data only have `alias1` entry from Contentful.

What I was trying is to add the codes to identify alias in `gatsby-config.js` using `windows.location.href`, and set `siteUrl` as dynamic, but it didn't work.

I am not sure it could be possible and how to implement it.

Thank you.