Add graphql introspection module

[mukesh-dream11]

This module probes for GraphQL endpoints, and attempts to extract schemas if found. The module itself is just a starting point, there can be further improvements added such as authentication and unit tests for this module.

[TheTechromancer]

@mukesh-dream11 thanks for the PR

@liquidsec this might be useful for lightfuzz

Also relevant: #766

[codecov]

Codecov Report

Attention: Patch coverage is 96.61017% with 2 lines in your changes missing coverage. Please review.

Project coverage is 93%. Comparing base (500d18d) to head (a9fa97d).

Files with missing lines	Patch %	Lines
bbot/modules/graphql_introspection.py	96%	2 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##             dev   #2515   +/-   ##
=====================================
- Coverage     93%     93%   -0%     
=====================================
  Files        400     402    +2     
  Lines      33184   33243   +59     
=====================================
+ Hits       30696   30730   +34     
- Misses      2488    2513   +25     

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[mukesh-dream11]

@TheTechromancer I've added unit tests and the web-basic flag to this module. Feel free to change flags if you believe this fits better under a different category. I believe web-basic is appropriate because this module is designed to send a maximum of 3 requests to any given root URL (sub-URLs are ignored for now).

I'm done with this PR, so I'm handing this off for review. :)