Bring back the v3 docs

[raphaelbadia]

ionic 4 is amazing but we need v3 docs brought back online

[Slypek]

Please use https://ionicframework.com/docs/v3/

[brandyshea]

We are working on updating the site to include this link, but please use the above link in the meantime. Thanks!

[brandyshea]

You should see the link to v3 docs in the upper right corner now: https://ionicframework.com/docs/

[ec6]

Thank you for the link.

There are still some issues on ionic v3 documentation linking to redirecting to ionic v4 documentation.

Example with the search docs link here. It is redirecting to v4 .