Make the crate #![no_std]

[FreezyLemon]

https://effective-rust.com/no-std.html says:

So: if your dependencies support it, and the simple transformations above are all that's needed, then consider making library code no_std compatible. When it is possible, it's not much additional work, and it allows for the widest reuse of the library.

Code changes are minimal, we don't need a std feature because nothing will be disabled without it. alloc is definitely required for Frame/Plane/AlignedData but that's still a smaller hurdle than the entire standard library.

println is now off the table for tests but that's not really a big limitation IMHO.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.41%. Comparing base (b8f193c) to head (687eacd).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #79   +/-   ##
=======================================
  Coverage   99.40%   99.41%           
=======================================
  Files           7        7           
  Lines         675      681    +6     
=======================================
+ Hits          671      677    +6     
  Misses          4        4           

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