Add redirects for working group pages

[xtqqczze]

Some old working-group URLs on rust-lang.org return 404s instead of redirecting to the correct location.

For example:

https://rust-lang.org/governance/wgs/wg-secure-code -> 404

but it should redirect to:

https://rust-lang.org/governance/teams/#team-wg-secure-code

[senekor]

I guess there would be several of these missing redirects? We'd have to figure out what change in the past invalidated the previous URLs so we can add all the necessary redirects.

[xtqqczze]

The pages started returning 404s sometime between 11 Sep 2025 and 13 Oct 2025.

https://web.archive.org/web/20250911054544/https://rust-lang.org/governance/wgs/wg-secure-code

[xtqqczze]

There is already a redirect for "governance/wgs" -> "governance#working-groups", so it seems we just need redirects for each individual WG.