Feature/graphql

[steffansluis]

This PR adds GraphQL functionality and tests.

[codecov]

Codecov Report

Merging #3 into master will decrease coverage by 13.33%.
The diff coverage is 86.66%.

@@             Coverage Diff             @@
##           master       #3       +/-   ##
===========================================
- Coverage     100%   86.66%   -13.34%     
===========================================
  Files           1        2        +1     
  Lines           1       15       +14     
  Branches        0        2        +2     
===========================================
+ Hits            1       13       +12     
- Misses          0        1        +1     
- Partials        0        1        +1

Impacted Files	Coverage Δ
src/index.ts	66.66% <66.66%> (-33.34%)	⬇️
src/graphql.ts	91.66% <91.66%> (ø)

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