Add length limit checks for CompoundTag and TreeRoot names

I am amazed we weren't checking this already. This ensures the error shows up in the place that caused it, and not when it gets encoded.

Bump shivammathur/setup-php in the github-actions group (#125)

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Improve documentation

Fix CS

JsonNbtParser: fixed TypeError being thrown when mixing ListTag value…

… types

CompoundTag: quietly ignore repeated keys, instead of throwing

this isn't ideal, but we don't have much of a choice; many chunks in very old PM worlds are affected by the furnace bug (basically any chunk with a furnace);
we have no other way to avoid losing the entire chunk to corruption errors

CompoundTag: repeat 3e0d9ef for 0.2 legacy

ListTag: fixed incorrect exception type thrown when encountering a no…

…n-empty list of TAG_End

Fixed PHPUnit deprecation warning