All docs links are for 0.5.0

[ChiaraGambone]

Going through the A-Frame school every link to the docs is for the 0.5.0 version.
Once you get on the 0.5.0 (such as https://aframe.io/docs/0.5.0/primitives/a-torus-knot.html) there is no quick way to get to the same page in 0.9.0
Clicking link "documentation for the current 0.9.0 version" brings to Introduction page.
Using the dropdown version selection on the left brings to Introduction page.

@ngokevin if i do a PR updating content.md will it be reviewed and merged?
I am asking since this repo isn't too active