Migrate wikipages relevant to game devs to site

Existing articles that just need to be extended.
[Console-Commands](https://github.com/beyond-all-reason/spring/wiki/Console-Commands) -> [guides/synced-commands](https://beyond-all-reason.github.io/spring/guides/synced-commands/)
[Engine-Settings-Config-File](https://github.com/beyond-all-reason/spring/wiki/Engine-Settings-Config-File) -> [guides/configuration-variables](https://beyond-all-reason.github.io/spring/guides/configuration-variables/)
[Lua_Handle](https://github.com/beyond-all-reason/spring/wiki/Lua_Handle) -> [api/LuaHandle](https://beyond-all-reason.github.io/spring/ldoc/modules/LuaHandle.html)
[Lua_SyncedControl](https://github.com/beyond-all-reason/spring/wiki/Lua_SyncedControl) -> [api/SyncedCtrl](https://beyond-all-reason.github.io/spring/ldoc/modules/SyncedCtrl.html)
[Lua_UnsyncedCtrl](https://github.com/beyond-all-reason/spring/wiki/Lua_UnsyncedCtrl) -> [api/UnsyncedCtrl](https://beyond-all-reason.github.io/spring/ldoc/modules/UnsyncedCtrl.html)
[Lua_UnsyncedRead](https://github.com/beyond-all-reason/spring/wiki/Lua_UnsyncedRead) -> [api/UnsyncedRead](https://beyond-all-reason.github.io/spring/ldoc/modules/UnsyncedRead.html)

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[Move-Definitions](https://github.com/beyond-all-reason/spring/wiki/Move-Definitions) - no article, but one is needed anyway to cover all the things that existed before Recoil (the wiki only lists diff vs Spring)
[Mod-Rules](https://github.com/beyond-all-reason/spring/wiki/Mod-Rules) - ditto, though there is an ongoing modrule flattening so wait until that is over

Compare the linked wiki articles with guides/synced-commands, guides/configuration-variables, and the LuaHandle, SyncedCtrl, UnsyncedCtrl, and UnsyncedRead API pages. Identify missing content before extending each destination; Move-Definitions needs a new article, while Mod-Rules should wait for the ongoing modrule flattening. Done means the relevant wiki material is represented on the site and both new topics are covered when ready.

Written by the indexing model from the issue text.