Add license scan report and status

[fossabot]

Your FOSSA integration was successful! Attached in this PR is a badge and license report to track scan status in your README.

Below are docs for integrating FOSSA license checks into your CI:

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[fossabot]

Your license scan is passing -- congrats!

Your badge status is now updated and ready to merge:

[codecov]

Codecov Report

Merging #2 into master will decrease coverage by 0.54%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             master      #2      +/-   ##
===========================================
- Coverage     85.84%   85.3%   -0.55%     
  Complexity       58      58              
===========================================
  Files             4       4              
  Lines           212     211       -1     
===========================================
- Hits            182     180       -2     
- Misses           30      31       +1

Impacted Files	Coverage Δ	Complexity Δ
src/OAuth.php	59.09% <0%> (-3.14%)	9% <0%> (ø)

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