Set correct content type of sitemap.xml

[stefankempf]

As explained in https://stackoverflow.com/questions/3272534/what-content-type-value-should-i-send-for-my-xml-sitemap

*Always target the /dev/ folder when proposing changes. *

Fixes # .

Changes proposed in this pull request:

[robdekort]

Thank you!

[sjclark]

Huh curious, I've always just used xml which Statamic by default automatically aliases to text/xml but from what I've just read up on application/xml is definitely a better choice. Wonder why it defaults to the other?

Edit: ironically just realised the article referenced above is one of the ones i read 😂

[robdekort]

I don't know either. I removed the content type - it was initially there - when Statamic added the XML template support, but Stefan found this still caused issues. At least on his server config. So it's back now :-)

[stefankempf]

Wonder why it defaults to the other?

I tried to find out myself but didn't found any answer. As stated in the article, sitemaps.org doesn't mention the content-type at all, so it was kind of a best guess from my side.