Link to documentation in the Wiki

[holke]

Link all function names in the Wiki to the documentation on the homepage - such that a user/developer is directly pointed to the docu.

In particular the article https://github.com/DLR-AMR/t8code/wiki/The-most-important-API-functions

Example:

Change "t8_cmesh_commit" to "t8_cmesh_commit"

related: would be good to have a "latest" version of the docs available per link, such that we automatically always link to the newest version.