Don't index deeplinks

[MattIPv4]

We need to ensure we do not allow indexing of deeplinks in search engines.

Eg. We can index the main site: github.io/dns-tool/ but we do not want to index github.io/dns-tool/?domain=somedodgy.site

[IAmJSD]

I don't think there is a way that this can be an issue. I believe this is all done on Google's side. With that being said, we should do some precautions since I don't know how trivial it is to force Google to index a page. I believe this has to be done by someone with access to the root directory though according to this documentation.

[MattIPv4]

I believe Google will wait for some JS to run when loading a page, so we could feasibly ensure we add a noindex meta tag if we detect a query param (or rather, whenever we have a non-default state, which gets stored as a query param). Not sure it'd be perfect, but it would be better than nothing.