chore: Change the confusing parameter position to a clear name. #637

[JSpiner]

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Fixes #637 🦕

It may be confusing that it is automatically updated by the position parameter. I renamed it to initialPosition to make it clear that it only works with the initial value.
(The compose foundation libraries also add the init prefix to the initial values ​​that go into rememberXXX.)

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[JSpiner]

I resolved the conflict.