docs(incentive-manager): add readme to incentive manager

[kerber0x]

Description and Motivation

This PR adds information about how the incentive manager works on a high level on a readme file.

Related Issues

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Checklist:

• I have read Migaloo's contribution guidelines.
• My pull request has a sound title and description (not something vague like Update index.md)
• All existing and new tests are passing.
• I updated/added relevant documentation.
• The code is formatted properly cargo fmt --all --.
• Clippy doesn't report any issues cargo clippy -- -D warnings.
• I have regenerated the schemas if needed cargo schema.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.15%. Comparing base (61ed894) to head (04a91a8).
Report is 1 commits behind head on release/v2_contracts.

Additional details and impacted files

@@                  Coverage Diff                  @@
##           release/v2_contracts     #354   +/-   ##
=====================================================
  Coverage                 91.15%   91.15%           
=====================================================
  Files                       279      279           
  Lines                     31119    31119           
=====================================================
  Hits                      28368    28368           
  Misses                     2751     2751           

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[0xFable]

Great work on this! 🚀 Left some suggestions on how to improve the flow and stuff
Make it as verbose as you can I'd say and at the end I will show you how to generate a markdown table of contents to make it easy to navigate even if its massive

[0xFable]

LGTM great job!! 🚀