Add unlink and unlink-2 icons.

[ericfennis]

Closes #26

[codecov]

Codecov Report

Merging #887 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##            master      #887   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            5         5           
  Lines           34        34           
  Branches         3         3           
=========================================
  Hits            34        34           

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