Wiki for documenting release process

[douglowe]

We want to have a central record of the process for making releases (and other documentation), that is associated with the repository, but isn't overfilling the readme file.

[steve-crouch]

Aleks' documented process for releases at: #472

[JaroCamphuijsen]

Where would this wiki live? It is also common to document this type of information in a README.dev.md file. Then at least it is version-controlled along with the rest of the code, in case the release process changes. Maintaining a separate wiki, can be cumbersome and will most likely lead to divergence between the source code and the process described in the wiki.