Deno command line tools

[nellh]

Adds command line tools for upload and download using Deno.

Some known issues:

• Hashing a dataset with a lot of annexed objects can take a while and doesn't show progress while hashing
• Broken symlinks throw an error
• Download only downloads git objects
• Needs CI for deno tests

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 65.31%. Comparing base (f07adfb) to head (ba3e27d).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3017   +/-   ##
=======================================
  Coverage   65.31%   65.31%           
=======================================
  Files         384      384           
  Lines       24670    24670           
  Branches      895      895           
=======================================
  Hits        16112    16112           
  Misses       8558     8558           

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[nellh]

Merging this so I can publish it on deno.land and I'll break out the remaining issue as a new issue.