[NTG-context] documenting namespaces and modules

After I got Wolfgang’s slides[1] and code example[2] from the “writing modules” workshop that I requested, I updated several wiki pages: * https://wiki.contextgarden.net/Modules * https://wiki.contextgarden.net/Module_Writing * https://wiki.contextgarden.net/Module_template * https://wiki.contextgarden.net/Module_Namespaces There are probably still errors or outdated relics left. Corrections appreciated. Hraban [1] https://meeting.contextgarden.net/2024/talks/wolfgang/module_howto.pdf [2] https://meeting.contextgarden.net/2024/talks/wolfgang/t-messenger.mkxl