This change adds documents to the view's document history Vec.
(This is used by `ga` for example to access the last buffer.)
Previously, a sequence like so would have confusing behavior:
1. Open file A: any document with an active language server
2. Find some definition that lives in another file - file B - with `gd`
3. Jump back in the jumplist with `C-o` to file A
4. Use `ga` intending to switch back to file B
The behavior prior to this change was that `ga` would switch to file
A: you could not use `ga` to switch to file B.