Update docs to expose redirectedFrom on $route object

[therealpecus]

This PR describes the vm.$route.redirectedFrom property that is made available if the current route is the result of a redirect.
It also updates the docs to clarify that props and meta fields are ignored for redirect route definitions.

[therealpecus]

A note on CI checks: no code being tested has been changed (this is a fork from develop), but I cannot relaunch the tests. Locally, all tests run fine.

[posva]

Hey, thanks for the PR and sorry for the delay.
I removed the note about ignoring props and meta field because I'm not sure what you're scenario you're talking about, do you mind sharing a fiddle showcasing what you mean so we can improve the docs?