docs: Old URLs throwing 404 instead of redirecting

[sidharthv96]

          > With this approach every documentation change will lead to broken links within live editor.

We have the redirects logic in the documentation site to handle this issue. But, I noticed that the redirect works locally, but throws 404 when deployed. So we'll need to fix that in the docs site, as there will be other sites that link to the docs.

Originally posted by @sidharthv96 in mermaid-js/mermaid-live-editor#1329 (comment)

[sidharthv96]

Duplicate #4989