Use terms like ExampleMod instead of FabricDocsReference for clarity

[hiisuuii]

Mentioned in Discord as well - I think it is worth examining whether the docs would be better off using names like example-mod and ExampleModInitializer in the example code rather than fabric-docs-reference and FabricDocsReference. I notice in the mod dev channels, that it seems to be a pretty common point of confusion. Many newcomers have been asking questions such as "what is FabricDocsReference?" and "where do I find FabricDocsReference?" because it is not immediately clear that these classes and names should be replaced with THEIR mod's ModInitializer class. I think the presence of "Fabric" in the class name causes people to believe it is some class provided by the API, rather than a class from their mod/the example mod.

[IMB11]

We're definitely considering this.