Adds missing workbox-sw redirect to d.c.c.

[malchata]

What's changed, or what was fixed?

• The guide at https://developers.google.com/web/tools/workbox/reference-docs/latest/workbox was deleted, but not redirected anywhere. This PR adds a redirect from that URL to point to https://developer.chrome.com/docs/workbox/modules/workbox-sw/

Fixes: #GoogleChrome/workbox#3059

Target Live Date: Within the next day or so would be fine.

• [ ] This has been reviewed and approved by (@jeffposnick)
• [x] I have run npm test locally and all tests pass (@malchata).
• [ ] I have added the appropriate type-something label.
• [x] I've staged the site and manually verified that my content displays correctly (@malchata).

CC: @petele @jeffposnick