Typelevel ecosystem broken links fix

[benkio]

related to the issue #4004

• Fix the 404 links
• Avoid redirections
• Add Fly4s
• upgrade shell.nix to the latest 21.05

links checked with https://validator.w3.org/checklink against the page https://typelevel.org/cats/typelevelEcosystem.html

I wasn't able to check it locally yet, having problems in generating the microsite, but this is up for visibility as draft
As soon as I solve the problems with the microsite generations I wish to test it following this article: https://matthewsetter.com/writing-tools/npm-broken-link-checker/

Cheers

[benkio]

this is what I see after moving to the branch and launching

nix-shell --pure
sbt docs/makeMicrosite

https://pastebin.com/u8DCNGHD

[rossabaker]

Thanks!

In a hurry now, but I think the microsite does not compile on the default scala version of the rest of the build. The ci.yml or old build runs should make clear which version works.

[benkio]

looking at ci.ymlI was able to generate the microsite, but only after upgrading nixpkgs to the last version in order to have access to later jekyll and ruby. I think we can move forward from the 18.09 release.

I runned linkchecker and this is the result of 5 min scanning

[rossabaker]

Nice work!

Markdown references could be used to DRY up FS2 or other repeated links, but it's not really that big a deal.

[benkio]

Nice work!

Markdown references could be used to DRY up FS2 or other repeated links, but it's not really that big a deal.

Just added the link references for duplicated links