feat: enable "std" feature for taffy

[frnsys]

What It Does

I was trying to print out a table but my program would panic with the error called Result::unwrap()on anErr value: CapacityError: insufficient capacity. This was due to that if taffy does not have its alloc or std features enabled then it uses arrays with a maximum capacity, which limits e.g. in my case the number of children a node can have. It didn't seem to me that the std feature was intentionally excluded so I added it in.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.14%. Comparing base (534d705) to head (f56fda4).
Report is 1 commits behind head on main.

Additional details and impacted files

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  Coverage   91.14%   91.14%           
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  Files          23       23           
  Lines        3445     3445           
  Branches     3445     3445           
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  Hits         3140     3140           
  Misses        238      238           
  Partials       67       67           

[ccbrown]

Thanks! std was excluded simply because it didn't seem necessary, but I hadn't encountered or considered this limitation.

I'll go ahead and cut a bug fix release with this change.