Fix the permalink for 1.5.1

[blakehawkins]

This is the URI referenced in https://github.com/scala-js/scala-js-website/blob/main/doc/internals/version-history.md

[gzm0]

TY for the PR. I'm assigning this to @sjrd, because I'm not 100% familiar with how these links are used / generated (I'd like to avoid removing an existing, incorrect permalink accidentally).

[sjrd]

Please add an appropriate redirect in
https://github.com/scala-js/scala-js-website/blob/main/.htaccess
in order not to break existing links elsewhere.

[blakehawkins]

The existing link is already a 404 so I think this PR doesn't actually add any exposure as-is

I'm happy to add a permalink redirect in any fase

[sjrd]

The existing URL https://www.scala-js.org/news/2020/11/16/announcing-scalajs-1.5.1/ is clearly not a 404. So if we move that page, we do need a redirect. 😉

[blakehawkins]

Yeah fair enough, assuming someone managed to get to that URI!

[gzm0]

It's very likely in a tweet somewhere :))