fix: adding reserved prefix to decode

[hopinheimer]

This was kinda odd issue I was struck while trying to solve this which required adding a new field, turns out the bytes field in BytesDiff was overlapping with Decode macro's fields

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.59%. Comparing base (5b6dd17) to head (9cfe6dd).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #51   +/-   ##
=======================================
  Coverage   75.59%   75.59%           
=======================================
  Files          13       13           
  Lines         795      795           
=======================================
  Hits          601      601           
  Misses        194      194           

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[michaelsproul]

I don't think we should modify the name of the struct field (it's not necessary).

[michaelsproul]

It would be good to add a regression test that exercises this change too. In the ssz_derive crate you could add a test which uses a struct with a field called bytes.