Feat #7: Support fetching branch data using GitHub API V4

[msvrtan]

This is using GraphQL API

[codecov-io]

Codecov Report

Merging #8 into master will decrease coverage by 9.2%.
The diff coverage is 67.39%.

@@             Coverage Diff             @@
##             master      #8      +/-   ##
===========================================
- Coverage      92.4%   83.2%   -9.21%     
- Complexity       41      59      +18     
===========================================
  Files            12      17       +5     
  Lines           158     250      +92     
===========================================
+ Hits            146     208      +62     
- Misses           12      42      +30

Impacted Files	Coverage Δ	Complexity Δ
src/V4/Repository/BranchApi.php	0% <0%> (ø)	4 <4> (?)
src/V4/Repository/Factory/BranchFactory.php	100% <100%> (ø)	2 <2> (?)
...pository/Factory/Commit/CommitCommitterFactory.php	100% <100%> (ø)	2 <2> (?)
src/V4/Repository/Factory/CommitFactory.php	69.44% <69.44%> (ø)	8 <8> (?)
.../Repository/Factory/Commit/CommitAuthorFactory.php	93.75% <93.75%> (ø)	2 <2> (?)

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