tests/thirdparty: add lukechampine/blake3

[mmcloughlin]

cc @lukechampine

Fixes #164

[codecov-commenter]

Codecov Report

Merging #231 (30426ef) into master (b76e849) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #231   +/-   ##
=======================================
  Coverage   76.16%   76.16%           
=======================================
  Files          65       65           
  Lines       20526    20526           
=======================================
  Hits        15633    15633           
  Misses       4814     4814           
  Partials       79       79           

Flag	Coverage Δ
integration	11.84% <ø> (ø)
stress	?
unittests	73.26% <ø> (ø)

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