Add Julia 1.6 and 1.7 to CI.yml

[MariaHei]

Fixes #80

[codecov]

Codecov Report

Merging #81 (8ae942b) into master (89774d9) will increase coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #81      +/-   ##
==========================================
+ Coverage   80.91%   80.95%   +0.03%     
==========================================
  Files          16       16              
  Lines        1457     1460       +3     
==========================================
+ Hits         1179     1182       +3     
  Misses        278      278              

Impacted Files	Coverage Δ
src/make_semantic_matrix.jl	83.83% <0.00%> (-0.42%)	⬇️
src/make_cue_matrix.jl	63.23% <0.00%> (+0.27%)	⬆️
src/find_path.jl	87.50% <0.00%> (+0.48%)	⬆️

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