refactor: Merge vanilla default files with normal config files

[Leguan16]

I do not like the current solution to the "how-to vanilla" page. Thats why I am proposing a refactor that merges the two files with adding a vanilla field to config options that alter the vanilla behavior.

only-merge-items-horizontally:
  vanilla: "true"
  default: "false"
  description: >-
    Prevents merging items that are not on the same y level, preventing potential
    visual artifacts.

I am aware of the unnecessary nodes showing no default value. Unfortunately, I did not yet find a way to get rid of them without major refactoring of already existing code. If you have suggestions, please share!

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