bip32 crate

[tony-iqlusion]

Initial implementation with secp256k1 derivation support

[codecov-commenter]

Codecov Report

Merging #670 (9d350f2) into main (5b29c2d) will increase coverage by 5.25%.
The diff coverage is 30.90%.

❗ Current head 9d350f2 differs from pull request most recent head 185f44d. Consider uploading reports for the commit 185f44d to get more accurate results

@@            Coverage Diff             @@
##             main     #670      +/-   ##
==========================================
+ Coverage   46.34%   51.60%   +5.25%     
==========================================
  Files          51       58       +7     
  Lines        1944     2087     +143     
==========================================
+ Hits          901     1077     +176     
+ Misses       1043     1010      -33     

Impacted Files	Coverage Δ
bip32/src/child_number.rs	0.00% <0.00%> (ø)
bip32/src/derivation_path.rs	0.00% <0.00%> (ø)
bip32/src/error.rs	0.00% <0.00%> (ø)
bip32/src/extended_secret_key.rs	0.00% <0.00%> (ø)
bip32/src/secret_key.rs	0.00% <0.00%> (ø)
hkd32/src/mnemonic/bits.rs	87.03% <ø> (+87.03%)	⬆️
hkd32/src/mnemonic/seed.rs	33.33% <ø> (+33.33%)	⬆️
hkd32/src/mnemonic/phrase.rs	72.54% <50.00%> (+72.54%)	⬆️
bip32/tests/bip39_vectors.rs	100.00% <100.00%> (ø)
bip32/tests/test_vectors.rs	100.00% <100.00%> (ø)
... and 17 more

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[prestwich]

nit: dervation paths are limited by spec to at most 256 elements, including the m. This type will allow invalid paths