Execute queries over GET

[rafalp]

Adds support for executing GraphQL queries sent over GET, as per spec.

Fixes #123

TODO

• ASGI
• WSGI
• Tests
• Changelog

[codecov]

Codecov Report

Attention: 4 lines in your changes are missing coverage. Please review.

Comparison is base (1698ed5) 97.88% compared to head (2cd2d01) 97.87%.
Report is 5 commits behind head on main.

Files	Patch %	Lines
ariadne/wsgi.py	90.90%	3 Missing ⚠️
ariadne/graphql.py	93.75%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1160      +/-   ##
==========================================
- Coverage   97.88%   97.87%   -0.02%     
==========================================
  Files         109      109              
  Lines        7905     8052     +147     
==========================================
+ Hits         7738     7881     +143     
- Misses        167      171       +4     

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